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THE DIAGNOSIS: Habit-Tic Deformity

Habit-tic deformity is a cause of nail dystrophy that commonly arises in children and adults due to subconscious repetitive and self-injurious manipulation of the nail bed or cuticle, which ultimately damages the nail matrix.^1,2 It can be considered a variant of onychotillomania.¹

Characteristic features of habit-tic deformity include a longitudinal depression on the central nail plate with transverse ridges,¹ which can be more prominent on the dominant hand.³ Patients typically note a long duration of nail deformity, often without insight into its etiology.² Diagnosis relies on careful assessment of the clinical presentation and the patient’s history to rule out other differential diagnoses. Based on our patient’s clinical presentation and history, we excluded wart, squamous cell carcinoma, eczema, psoriasis, lichen planus, autoimmune connective tissue disease, onychomycosis, paronychia, pincer nail deformity, and Beau line as potential diagnoses. Biopsy also can be performed to exclude these diagnoses from the differential if the cause is unclear following clinical examination.

Treatment for habit-tic deformity involves identifying and addressing the underlying habit. Barrier methods such as bandages and cyanoacrylate adhesives that prevent further manipulation of the nail matrix are effective treatments for habit-tic deformity.² A multidisciplinary approach with psychiatry may be optimal to identify underlying psychological comorbidities and break the habit through behavior interventions and medications.⁴ Nail dystrophy generally improves once the habit is disrupted; however, a younger age of onset may carry a worse prognosis.³ Patients should be counseled that the affected nail may never grow normally.

Our patient was advised to use fluocinonide ointment 0.05% to reduce inflammation of the proximal nail fold and to cover the thumbnail with a bandage to prevent picking. He also was counseled that the nail may show ongoing abnormal growth. Minimal improvement was noted after 6 months.

THE DIAGNOSIS: Habit-Tic Deformity

Habit-tic deformity is a cause of nail dystrophy that commonly arises in children and adults due to subconscious repetitive and self-injurious manipulation of the nail bed or cuticle, which ultimately damages the nail matrix.^1,2 It can be considered a variant of onychotillomania.¹

Characteristic features of habit-tic deformity include a longitudinal depression on the central nail plate with transverse ridges,¹ which can be more prominent on the dominant hand.³ Patients typically note a long duration of nail deformity, often without insight into its etiology.² Diagnosis relies on careful assessment of the clinical presentation and the patient’s history to rule out other differential diagnoses. Based on our patient’s clinical presentation and history, we excluded wart, squamous cell carcinoma, eczema, psoriasis, lichen planus, autoimmune connective tissue disease, onychomycosis, paronychia, pincer nail deformity, and Beau line as potential diagnoses. Biopsy also can be performed to exclude these diagnoses from the differential if the cause is unclear following clinical examination.

Treatment for habit-tic deformity involves identifying and addressing the underlying habit. Barrier methods such as bandages and cyanoacrylate adhesives that prevent further manipulation of the nail matrix are effective treatments for habit-tic deformity.² A multidisciplinary approach with psychiatry may be optimal to identify underlying psychological comorbidities and break the habit through behavior interventions and medications.⁴ Nail dystrophy generally improves once the habit is disrupted; however, a younger age of onset may carry a worse prognosis.³ Patients should be counseled that the affected nail may never grow normally.

Our patient was advised to use fluocinonide ointment 0.05% to reduce inflammation of the proximal nail fold and to cover the thumbnail with a bandage to prevent picking. He also was counseled that the nail may show ongoing abnormal growth. Minimal improvement was noted after 6 months.

THE DIAGNOSIS: Habit-Tic Deformity

Habit-tic deformity is a cause of nail dystrophy that commonly arises in children and adults due to subconscious repetitive and self-injurious manipulation of the nail bed or cuticle, which ultimately damages the nail matrix.^1,2 It can be considered a variant of onychotillomania.¹

Characteristic features of habit-tic deformity include a longitudinal depression on the central nail plate with transverse ridges,¹ which can be more prominent on the dominant hand.³ Patients typically note a long duration of nail deformity, often without insight into its etiology.² Diagnosis relies on careful assessment of the clinical presentation and the patient’s history to rule out other differential diagnoses. Based on our patient’s clinical presentation and history, we excluded wart, squamous cell carcinoma, eczema, psoriasis, lichen planus, autoimmune connective tissue disease, onychomycosis, paronychia, pincer nail deformity, and Beau line as potential diagnoses. Biopsy also can be performed to exclude these diagnoses from the differential if the cause is unclear following clinical examination.

Treatment for habit-tic deformity involves identifying and addressing the underlying habit. Barrier methods such as bandages and cyanoacrylate adhesives that prevent further manipulation of the nail matrix are effective treatments for habit-tic deformity.² A multidisciplinary approach with psychiatry may be optimal to identify underlying psychological comorbidities and break the habit through behavior interventions and medications.⁴ Nail dystrophy generally improves once the habit is disrupted; however, a younger age of onset may carry a worse prognosis.³ Patients should be counseled that the affected nail may never grow normally.

Our patient was advised to use fluocinonide ointment 0.05% to reduce inflammation of the proximal nail fold and to cover the thumbnail with a bandage to prevent picking. He also was counseled that the nail may show ongoing abnormal growth. Minimal improvement was noted after 6 months.

THE DIAGNOSIS: Acral Hemorrhagic Darier Disease

Darier disease (DD), also known as keratosis follicularis, is a rare autosomal-dominant genodermatosis caused by mutations in the ATPase sarcoplasmic/endoplasmic reticulum Ca2+ transporting 2 gene (ATP2A2). This gene encodes the enzyme sarcoplasmic/endoplasmic reticulum calcium ATPase 2, which results in abnormal calcium signaling in keratinocytes and leads to dyskeratosis.¹ Darier disease commonly manifests in the second decade of life with hyperkeratotic papules coalescing into plaques, often accompanied by erosions and fissures that cause discomfort and pruritus. Darier disease also is associated with characteristic nail findings such as the classic candy cane nails and V-shaped nicking.

Acral hemorrhagic lesions are a rare manifestation of DD. Clinically, these lesions can manifest as hemorrhagic macules, papules, and/or vesicles, most commonly occurring following local trauma or retinoid use. Patients with these lesions are believed to have either specific mutations in the ATP2A2 gene that impair sarcoplasmic/endoplasmic reticulum calcium ATPase 2 function in the vascular endothelium or a mutation in the sarcoplasmic/endoplasmic reticulum calcium ATPase protein itself, leading to dysregulation of mitochondrial homeostasis from within the cell, provoking oxidative stress and causing detrimental effects on blood vessels.² Patients with this variant can present with all the features of classic DD concomitantly, with varying symptom severity or distinct clinical features during separate episodic flares, or as the sole manifestation. Other nonclassical lesions of DD include acral keratoderma, giant comedones, keloidlike vegetations, and leucodermic macules (Figure).³

Acral hemorrhagic DD may appear either in isolation or in tandem with more traditional symptoms, necessitating consideration of other possible differential diagnoses such as acrokeratosis verruciformis of Hopf (AKV), porphyria cutanea tarda, bullous lichen planus (BLP), and hemorrhagic lichen sclerosus.

Sometimes regarded as a variant of DD, AKV is an autosomal- dominant genodermatosis characterized by flat or verrucous hyperkeratotic papules on the hands and feet. In AKV, the nails also may be affected, with changes including striations, subungual hyperkeratosis, and V-shaped nicking of the distal nails. Although our patient displayed features of AKV, it has not been associated with acral hemorrhagic macules, making this diagnosis less likely than DD.⁴

Porphyria cutanea tarda, a condition caused by decreased levels of uroporphyrinogen decarboxylase, also can cause skin manifestations such as blistering as well as increased skin fragility, predominantly in sun-exposed areas.⁵ Our patient’s lack of photosensitivity and absence of other common symptoms of this disorder, such as hypertrichosis and hyperpigmentation, made porphyria cutanea tarda less likely.

Bullous lichen planus is a rare subtype of lichen planus characterized by tense bullae arising from preexisting lichen planus lesions or appearing de novo, most commonly manifesting on the oral mucosa or the legs.⁶ The bullae associated with BLP can rupture and form ulcers—a symptom that could potentially be mistaken for hemorrhagic macules like the ones observed in our patient. However, BLP typically is characterized by erythematous, violaceous, polygonal papules commonly appearing on the oral mucosa and the legs with blisters developing near or on pre-existing lichen planus lesions. These are different from the hyperkeratotic papules and leucodermic macules seen in our patient, which aligned more closely with the clinical presentation of DD.

Hemorrhagic lichen sclerosus presents with white atrophic patches and plaques and hemorrhagic bullae, which may resemble the leucodermic macules and hemorrhagic macules of DD. However, hemorrhagic lichen sclerosus most commonly involves the genital area in postmenopausal women. Extragenital manifestations of lichen sclerosus, although less common, can occur and typically manifest on the thighs, buttocks, breasts, back, chest, axillae, shoulders, and wrists.⁷ Notably, these hemorrhagic lesions typically are surrounded by hypopigmented skin and display an atrophic appearance.

Management of DD can be challenging. General measures include sun protection, heat avoidance, and friction reduction. Retinoids are considered the first-line therapy for severe DD, as they help normalize keratinocyte differentiation and reduce keratotic scaling.⁸ Topical corticosteroids can help manage inflammation and reduce the risk for secondary infections. Our patient responded well to this treatment approach, with a notable reduction in the number and severity of the hyperkeratotic plaques and resolution of the acral hemorrhagic lesions.

THE DIAGNOSIS: Acral Hemorrhagic Darier Disease

Darier disease (DD), also known as keratosis follicularis, is a rare autosomal-dominant genodermatosis caused by mutations in the ATPase sarcoplasmic/endoplasmic reticulum Ca2+ transporting 2 gene (ATP2A2). This gene encodes the enzyme sarcoplasmic/endoplasmic reticulum calcium ATPase 2, which results in abnormal calcium signaling in keratinocytes and leads to dyskeratosis.¹ Darier disease commonly manifests in the second decade of life with hyperkeratotic papules coalescing into plaques, often accompanied by erosions and fissures that cause discomfort and pruritus. Darier disease also is associated with characteristic nail findings such as the classic candy cane nails and V-shaped nicking.

Acral hemorrhagic lesions are a rare manifestation of DD. Clinically, these lesions can manifest as hemorrhagic macules, papules, and/or vesicles, most commonly occurring following local trauma or retinoid use. Patients with these lesions are believed to have either specific mutations in the ATP2A2 gene that impair sarcoplasmic/endoplasmic reticulum calcium ATPase 2 function in the vascular endothelium or a mutation in the sarcoplasmic/endoplasmic reticulum calcium ATPase protein itself, leading to dysregulation of mitochondrial homeostasis from within the cell, provoking oxidative stress and causing detrimental effects on blood vessels.² Patients with this variant can present with all the features of classic DD concomitantly, with varying symptom severity or distinct clinical features during separate episodic flares, or as the sole manifestation. Other nonclassical lesions of DD include acral keratoderma, giant comedones, keloidlike vegetations, and leucodermic macules (Figure).³

Acral hemorrhagic DD may appear either in isolation or in tandem with more traditional symptoms, necessitating consideration of other possible differential diagnoses such as acrokeratosis verruciformis of Hopf (AKV), porphyria cutanea tarda, bullous lichen planus (BLP), and hemorrhagic lichen sclerosus.

Sometimes regarded as a variant of DD, AKV is an autosomal- dominant genodermatosis characterized by flat or verrucous hyperkeratotic papules on the hands and feet. In AKV, the nails also may be affected, with changes including striations, subungual hyperkeratosis, and V-shaped nicking of the distal nails. Although our patient displayed features of AKV, it has not been associated with acral hemorrhagic macules, making this diagnosis less likely than DD.⁴

Porphyria cutanea tarda, a condition caused by decreased levels of uroporphyrinogen decarboxylase, also can cause skin manifestations such as blistering as well as increased skin fragility, predominantly in sun-exposed areas.⁵ Our patient’s lack of photosensitivity and absence of other common symptoms of this disorder, such as hypertrichosis and hyperpigmentation, made porphyria cutanea tarda less likely.

Bullous lichen planus is a rare subtype of lichen planus characterized by tense bullae arising from preexisting lichen planus lesions or appearing de novo, most commonly manifesting on the oral mucosa or the legs.⁶ The bullae associated with BLP can rupture and form ulcers—a symptom that could potentially be mistaken for hemorrhagic macules like the ones observed in our patient. However, BLP typically is characterized by erythematous, violaceous, polygonal papules commonly appearing on the oral mucosa and the legs with blisters developing near or on pre-existing lichen planus lesions. These are different from the hyperkeratotic papules and leucodermic macules seen in our patient, which aligned more closely with the clinical presentation of DD.

Hemorrhagic lichen sclerosus presents with white atrophic patches and plaques and hemorrhagic bullae, which may resemble the leucodermic macules and hemorrhagic macules of DD. However, hemorrhagic lichen sclerosus most commonly involves the genital area in postmenopausal women. Extragenital manifestations of lichen sclerosus, although less common, can occur and typically manifest on the thighs, buttocks, breasts, back, chest, axillae, shoulders, and wrists.⁷ Notably, these hemorrhagic lesions typically are surrounded by hypopigmented skin and display an atrophic appearance.

Management of DD can be challenging. General measures include sun protection, heat avoidance, and friction reduction. Retinoids are considered the first-line therapy for severe DD, as they help normalize keratinocyte differentiation and reduce keratotic scaling.⁸ Topical corticosteroids can help manage inflammation and reduce the risk for secondary infections. Our patient responded well to this treatment approach, with a notable reduction in the number and severity of the hyperkeratotic plaques and resolution of the acral hemorrhagic lesions.

THE DIAGNOSIS: Acral Hemorrhagic Darier Disease

Darier disease (DD), also known as keratosis follicularis, is a rare autosomal-dominant genodermatosis caused by mutations in the ATPase sarcoplasmic/endoplasmic reticulum Ca2+ transporting 2 gene (ATP2A2). This gene encodes the enzyme sarcoplasmic/endoplasmic reticulum calcium ATPase 2, which results in abnormal calcium signaling in keratinocytes and leads to dyskeratosis.¹ Darier disease commonly manifests in the second decade of life with hyperkeratotic papules coalescing into plaques, often accompanied by erosions and fissures that cause discomfort and pruritus. Darier disease also is associated with characteristic nail findings such as the classic candy cane nails and V-shaped nicking.

Acral hemorrhagic lesions are a rare manifestation of DD. Clinically, these lesions can manifest as hemorrhagic macules, papules, and/or vesicles, most commonly occurring following local trauma or retinoid use. Patients with these lesions are believed to have either specific mutations in the ATP2A2 gene that impair sarcoplasmic/endoplasmic reticulum calcium ATPase 2 function in the vascular endothelium or a mutation in the sarcoplasmic/endoplasmic reticulum calcium ATPase protein itself, leading to dysregulation of mitochondrial homeostasis from within the cell, provoking oxidative stress and causing detrimental effects on blood vessels.² Patients with this variant can present with all the features of classic DD concomitantly, with varying symptom severity or distinct clinical features during separate episodic flares, or as the sole manifestation. Other nonclassical lesions of DD include acral keratoderma, giant comedones, keloidlike vegetations, and leucodermic macules (Figure).³

Acral hemorrhagic DD may appear either in isolation or in tandem with more traditional symptoms, necessitating consideration of other possible differential diagnoses such as acrokeratosis verruciformis of Hopf (AKV), porphyria cutanea tarda, bullous lichen planus (BLP), and hemorrhagic lichen sclerosus.

Sometimes regarded as a variant of DD, AKV is an autosomal- dominant genodermatosis characterized by flat or verrucous hyperkeratotic papules on the hands and feet. In AKV, the nails also may be affected, with changes including striations, subungual hyperkeratosis, and V-shaped nicking of the distal nails. Although our patient displayed features of AKV, it has not been associated with acral hemorrhagic macules, making this diagnosis less likely than DD.⁴

Porphyria cutanea tarda, a condition caused by decreased levels of uroporphyrinogen decarboxylase, also can cause skin manifestations such as blistering as well as increased skin fragility, predominantly in sun-exposed areas.⁵ Our patient’s lack of photosensitivity and absence of other common symptoms of this disorder, such as hypertrichosis and hyperpigmentation, made porphyria cutanea tarda less likely.

Bullous lichen planus is a rare subtype of lichen planus characterized by tense bullae arising from preexisting lichen planus lesions or appearing de novo, most commonly manifesting on the oral mucosa or the legs.⁶ The bullae associated with BLP can rupture and form ulcers—a symptom that could potentially be mistaken for hemorrhagic macules like the ones observed in our patient. However, BLP typically is characterized by erythematous, violaceous, polygonal papules commonly appearing on the oral mucosa and the legs with blisters developing near or on pre-existing lichen planus lesions. These are different from the hyperkeratotic papules and leucodermic macules seen in our patient, which aligned more closely with the clinical presentation of DD.

Hemorrhagic lichen sclerosus presents with white atrophic patches and plaques and hemorrhagic bullae, which may resemble the leucodermic macules and hemorrhagic macules of DD. However, hemorrhagic lichen sclerosus most commonly involves the genital area in postmenopausal women. Extragenital manifestations of lichen sclerosus, although less common, can occur and typically manifest on the thighs, buttocks, breasts, back, chest, axillae, shoulders, and wrists.⁷ Notably, these hemorrhagic lesions typically are surrounded by hypopigmented skin and display an atrophic appearance.

Management of DD can be challenging. General measures include sun protection, heat avoidance, and friction reduction. Retinoids are considered the first-line therapy for severe DD, as they help normalize keratinocyte differentiation and reduce keratotic scaling.⁸ Topical corticosteroids can help manage inflammation and reduce the risk for secondary infections. Our patient responded well to this treatment approach, with a notable reduction in the number and severity of the hyperkeratotic plaques and resolution of the acral hemorrhagic lesions.

THE DIAGNOSIS: Chemotherapy-Induced Flagellate Dermatitis

Based on the clinical presentation and temporal relation with chemotherapy, a diagnosis of bleomycininduced flagellate dermatitis (FD) was made, as bleomycin is the only chemotherapeutic agent from this regimen that has been linked with FD.^1,2 Laboratory findings revealed eosinophilia, further supporting a druginduced dermatitis. The patient was treated with oral steroids and diphenhydramine to alleviate itching and discomfort. The chemotherapy was temporarily discontinued until symptomatic improvement was observed within 2 to 3 days.

Flagellate dermatitis is characterized by unique erythematous, linear, intermingled streaks of adjoining firm papules—often preceded by a prodrome of global pruritus—that eventually become hyperpigmented as the erythema subsides. The clinical manifestation of FD can be idiopathic; true/mechanical (dermatitis artefacta, abuse, sadomasochism); chemotherapy induced (peplomycin, trastuzumab, cisplatin, docetaxel, bendamustine); toxin induced (shiitake mushroom, cnidarian stings, Paederus insects); related to rheumatologic diseases (dermatomyositis, adult-onset Still disease), dermatographism, phytophotodermatitis, or poison ivy dermatitis; or induced by chikungunya fever.¹

The term flagellate originates from the Latin word flagellum, which pertains to the distinctive whiplike pattern. It was first described by Moulin et al³ in 1970 in reference to bleomycin-induced linear hyperpigmentation. Bleomycin, a glycopeptide antibiotic derived from Streptomyces verticillus, is used to treat Hodgkin lymphoma, squamous cell carcinoma, and germ cell tumors. The worldwide incidence of bleomycin-induced FD is 8% to 22% and commonly is associated with a cumulative dose greater than 100 U.² Clinical presentation is variable in terms of onset, distribution, and morphology of the eruption and could be independent of dose, route of administration, or type of malignancy being treated. The flagellate rash commonly involves the trunk, arms, and legs; can develop within hours to 6 months of starting bleomycin therapy; often is preceded by generalized itching; and eventually heals with hyperpigmentation.

Possible mechanisms of bleomycin-induced FD include localized melanogenesis, inflammatory pigmentary incontinence, alterations to normal pigmentation patterns, cytotoxic effects of the drug itself, minor trauma/ scratching leading to increased blood flow and causing local accumulation of bleomycin, heat recall, and reduced epidermal turnover leading to extended interaction between keratinocytes and melanocytes.² Heat exposure can act as a trigger for bleomycin-induced skin rash recall even months after the treatment is stopped.

Apart from discontinuing the drug, there is no specific treatment available for bleomycin-induced FD. The primary objective of treatment is to alleviate pruritus, which often involves the use of topical or systemic corticosteroids and oral antihistamines. The duration of treatment depends on the patient’s clinical response. Once treatment is discontinued, FD typically resolves within 6 to 8 months. However, there can be a permanent postinflammatory hyperpigmentation in the affected area.⁴ Although there is a concern for increased mortality after postponement of chemotherapy,⁵ the decision to proceed with or discontinue the chemotherapy regimen necessitates a comprehensive interdisciplinary discussion and a meticulous assessment of the risks and benefits that is customized to each individual patient. Flagellate dermatitis can reoccur with bleomycin re-exposure; a combined approach of proactive topical and systemic steroid treatment seems to diminish the likelihood of FD recurrence.⁵

Our case underscores the importance of recognizing, detecting, and managing FD promptly in individuals undergoing bleomycin-based chemotherapy. Medical professionals should familiarize themselves with this distinct adverse effect linked to bleomycin, enabling prompt discontinuation if necessary, and educate patients about the condition’s typically temporary nature, thereby alleviating their concerns.

THE DIAGNOSIS: Chemotherapy-Induced Flagellate Dermatitis

Based on the clinical presentation and temporal relation with chemotherapy, a diagnosis of bleomycininduced flagellate dermatitis (FD) was made, as bleomycin is the only chemotherapeutic agent from this regimen that has been linked with FD.^1,2 Laboratory findings revealed eosinophilia, further supporting a druginduced dermatitis. The patient was treated with oral steroids and diphenhydramine to alleviate itching and discomfort. The chemotherapy was temporarily discontinued until symptomatic improvement was observed within 2 to 3 days.

Flagellate dermatitis is characterized by unique erythematous, linear, intermingled streaks of adjoining firm papules—often preceded by a prodrome of global pruritus—that eventually become hyperpigmented as the erythema subsides. The clinical manifestation of FD can be idiopathic; true/mechanical (dermatitis artefacta, abuse, sadomasochism); chemotherapy induced (peplomycin, trastuzumab, cisplatin, docetaxel, bendamustine); toxin induced (shiitake mushroom, cnidarian stings, Paederus insects); related to rheumatologic diseases (dermatomyositis, adult-onset Still disease), dermatographism, phytophotodermatitis, or poison ivy dermatitis; or induced by chikungunya fever.¹

The term flagellate originates from the Latin word flagellum, which pertains to the distinctive whiplike pattern. It was first described by Moulin et al³ in 1970 in reference to bleomycin-induced linear hyperpigmentation. Bleomycin, a glycopeptide antibiotic derived from Streptomyces verticillus, is used to treat Hodgkin lymphoma, squamous cell carcinoma, and germ cell tumors. The worldwide incidence of bleomycin-induced FD is 8% to 22% and commonly is associated with a cumulative dose greater than 100 U.² Clinical presentation is variable in terms of onset, distribution, and morphology of the eruption and could be independent of dose, route of administration, or type of malignancy being treated. The flagellate rash commonly involves the trunk, arms, and legs; can develop within hours to 6 months of starting bleomycin therapy; often is preceded by generalized itching; and eventually heals with hyperpigmentation.

Possible mechanisms of bleomycin-induced FD include localized melanogenesis, inflammatory pigmentary incontinence, alterations to normal pigmentation patterns, cytotoxic effects of the drug itself, minor trauma/ scratching leading to increased blood flow and causing local accumulation of bleomycin, heat recall, and reduced epidermal turnover leading to extended interaction between keratinocytes and melanocytes.² Heat exposure can act as a trigger for bleomycin-induced skin rash recall even months after the treatment is stopped.

Apart from discontinuing the drug, there is no specific treatment available for bleomycin-induced FD. The primary objective of treatment is to alleviate pruritus, which often involves the use of topical or systemic corticosteroids and oral antihistamines. The duration of treatment depends on the patient’s clinical response. Once treatment is discontinued, FD typically resolves within 6 to 8 months. However, there can be a permanent postinflammatory hyperpigmentation in the affected area.⁴ Although there is a concern for increased mortality after postponement of chemotherapy,⁵ the decision to proceed with or discontinue the chemotherapy regimen necessitates a comprehensive interdisciplinary discussion and a meticulous assessment of the risks and benefits that is customized to each individual patient. Flagellate dermatitis can reoccur with bleomycin re-exposure; a combined approach of proactive topical and systemic steroid treatment seems to diminish the likelihood of FD recurrence.⁵

Our case underscores the importance of recognizing, detecting, and managing FD promptly in individuals undergoing bleomycin-based chemotherapy. Medical professionals should familiarize themselves with this distinct adverse effect linked to bleomycin, enabling prompt discontinuation if necessary, and educate patients about the condition’s typically temporary nature, thereby alleviating their concerns.

THE DIAGNOSIS: Chemotherapy-Induced Flagellate Dermatitis

Based on the clinical presentation and temporal relation with chemotherapy, a diagnosis of bleomycininduced flagellate dermatitis (FD) was made, as bleomycin is the only chemotherapeutic agent from this regimen that has been linked with FD.^1,2 Laboratory findings revealed eosinophilia, further supporting a druginduced dermatitis. The patient was treated with oral steroids and diphenhydramine to alleviate itching and discomfort. The chemotherapy was temporarily discontinued until symptomatic improvement was observed within 2 to 3 days.

Flagellate dermatitis is characterized by unique erythematous, linear, intermingled streaks of adjoining firm papules—often preceded by a prodrome of global pruritus—that eventually become hyperpigmented as the erythema subsides. The clinical manifestation of FD can be idiopathic; true/mechanical (dermatitis artefacta, abuse, sadomasochism); chemotherapy induced (peplomycin, trastuzumab, cisplatin, docetaxel, bendamustine); toxin induced (shiitake mushroom, cnidarian stings, Paederus insects); related to rheumatologic diseases (dermatomyositis, adult-onset Still disease), dermatographism, phytophotodermatitis, or poison ivy dermatitis; or induced by chikungunya fever.¹

The term flagellate originates from the Latin word flagellum, which pertains to the distinctive whiplike pattern. It was first described by Moulin et al³ in 1970 in reference to bleomycin-induced linear hyperpigmentation. Bleomycin, a glycopeptide antibiotic derived from Streptomyces verticillus, is used to treat Hodgkin lymphoma, squamous cell carcinoma, and germ cell tumors. The worldwide incidence of bleomycin-induced FD is 8% to 22% and commonly is associated with a cumulative dose greater than 100 U.² Clinical presentation is variable in terms of onset, distribution, and morphology of the eruption and could be independent of dose, route of administration, or type of malignancy being treated. The flagellate rash commonly involves the trunk, arms, and legs; can develop within hours to 6 months of starting bleomycin therapy; often is preceded by generalized itching; and eventually heals with hyperpigmentation.

Possible mechanisms of bleomycin-induced FD include localized melanogenesis, inflammatory pigmentary incontinence, alterations to normal pigmentation patterns, cytotoxic effects of the drug itself, minor trauma/ scratching leading to increased blood flow and causing local accumulation of bleomycin, heat recall, and reduced epidermal turnover leading to extended interaction between keratinocytes and melanocytes.² Heat exposure can act as a trigger for bleomycin-induced skin rash recall even months after the treatment is stopped.

Apart from discontinuing the drug, there is no specific treatment available for bleomycin-induced FD. The primary objective of treatment is to alleviate pruritus, which often involves the use of topical or systemic corticosteroids and oral antihistamines. The duration of treatment depends on the patient’s clinical response. Once treatment is discontinued, FD typically resolves within 6 to 8 months. However, there can be a permanent postinflammatory hyperpigmentation in the affected area.⁴ Although there is a concern for increased mortality after postponement of chemotherapy,⁵ the decision to proceed with or discontinue the chemotherapy regimen necessitates a comprehensive interdisciplinary discussion and a meticulous assessment of the risks and benefits that is customized to each individual patient. Flagellate dermatitis can reoccur with bleomycin re-exposure; a combined approach of proactive topical and systemic steroid treatment seems to diminish the likelihood of FD recurrence.⁵

Our case underscores the importance of recognizing, detecting, and managing FD promptly in individuals undergoing bleomycin-based chemotherapy. Medical professionals should familiarize themselves with this distinct adverse effect linked to bleomycin, enabling prompt discontinuation if necessary, and educate patients about the condition’s typically temporary nature, thereby alleviating their concerns.

THE DIAGNOSIS: Ectopic (Accessory) Breast Tissue

Ectopic (accessory) breast tissue (EBT) is a phenomenon caused by failed regression of one or more components of the embryonic mammary ridges— paired ectodermal thickenings that eventually develop into definitive breast tissue including the nipples, areolae, and parenchyma. Ectopic breast tissue is more common in women than men and is believed to be sporadic, although an autosomal-dominant inheritance mechanism with incomplete penetrance has been proposed for some cases.¹ The reported incidence of EBT varies greatly among racial and ethnic groups but is most common in individuals of Asian descent. The incidence across all types of EBT is estimated at 0.25% to 6% in the general population.²

Observed clinical variations of EBT range from simple polythelia (additional nipple[s] without associated parenchyma) to complete polymastia (organized and differentiated accessory breasts). Some types of EBT are rarer than others: One report of gynecologic cancer screenings in 1660 patients found polymastia and polythelia incidences of 0.12% and 5.48%, respectively.³ Of the symptomatic variations, isolated parenchymal EBT without a nipple or areolar complex is the most common and may manifest clinically as unilateral or bilateral tender, mildly erythematous nodules or masses often located in the axillae. Ectopic breast tissue generally is observed along the milk line, a developmental regional designation corresponding to the embryologic mammary ridge and extending linearly from the anterior axilla to the inguinal fold on both sides of the body; however, there have been rare reports of EBT manifesting in areas outside the milk line, such as the face, neck, back, vulva, and extremities.^2,3

Given that the underlying elements of EBT usually are hormone responsive (as with normal breast tissue), the initial symptom onset and subsequent manifestation frequently coincide with pubertal milestones, pregnancy, or lactation. Furthermore, some patients with EBT may experience symptom fluctuations in concordance with monthly menstrual phases. Many cases of EBT are selflimited and resolve within weeks to months after the end of a pregnancy or lactation, but some cases may persist. Continued observation and follow-up are advisable in all patients, as EBT symptoms often recur and the tissue is susceptible to the same disease processes that affect normal breasts, the most concerning of which is malignancy.⁴ Although the true incidence is limited by available data, primary ectopic breast malignancy has been estimated to account for 0.3% to 3.8% of diagnosed breast malignancies.² Cases of malignancy arising from EBT often are of higher grade and poorer prognosis, a finding that may be attributable to diagnostic delays caused by oversight or misdiagnosis of EBT rather than inherent differences in the biologic profile of the tumors.^2,4 Patients with a documented history of EBT may benefit from having their routine breast cancer screenings expanded to include areas with EBT foci.

Potential misdiagnoses for EBT include subcutaneous lipoma, axillary lymphadenopathy, abscess, hidradenitis suppurativa, or malignancy. Features that are suggestive of EBT include symptom association with hormone fluctuations (eg, menstrual phases), absence of fever, and lactescent rather than purulent drainage. Among reported EBT cases, spontaneous lactation rarely is described and, if present, often is associated with a history of prior trauma (eg, core needle biopsy or local abscess formation).⁵ This trauma creates an aberrant connection known as a milk fistula between the underlying parenchyma and the skin surface. Interestingly, our patient denied any history of axillary trauma, but she was noted to be lactating from an apparent milk fistula rather than an organized secretory duct system.

Though a patient history and clinical examination may be sufficient to diagnose EBT cases that are more physically apparent and well correlated with hormone fluctuations, many cases require additional diagnostic studies for confirmation. Of the tools available, ultrasonography generally is considered first-line due to its noninvasive nature, low cost, minimal risk, and high diagnostic value.² Ultrasonography quickly differentiates between abscesses and cystlike processes, which may appear as discrete areas of decreased echogenicity, and breast tissue, which manifests with fibroglandular tissue and lobules of fat.^2,6 Additionally, ultrasonography may demonstrate the secretion of milk through ducts or fistulae, if present. Should examination with ultrasonography prove inconclusive, follow-up studies using conventional radiographic mammography or magnetic resonance imaging may be warranted. Biopsy of EBT foci generally is not indicated unless first-line noninvasive studies fail to yield a conclusive diagnosis; however, biopsy also may be warranted if initial imaging is suggestive of malignancy arising from EBT.²

Management of EBT generally is conservative, and symptoms often resolve without intervention.⁴ Symptomatic relief may be achieved through techniques such as application of warm/cold compresses, avoidance of mechanical stimulation, and use of over-the-counter pain medicine. In cases that are persistent, frequently recurrent, or associated with severe symptoms or that cause considerable cosmetic impact, management with surgical excision and/or liposuction may be warranted.⁷ In our patient, the symptoms were not bothersome enough to warrant surgical intervention, so she was managed conservatively and did not return for follow-up.

THE DIAGNOSIS: Ectopic (Accessory) Breast Tissue

Ectopic (accessory) breast tissue (EBT) is a phenomenon caused by failed regression of one or more components of the embryonic mammary ridges— paired ectodermal thickenings that eventually develop into definitive breast tissue including the nipples, areolae, and parenchyma. Ectopic breast tissue is more common in women than men and is believed to be sporadic, although an autosomal-dominant inheritance mechanism with incomplete penetrance has been proposed for some cases.¹ The reported incidence of EBT varies greatly among racial and ethnic groups but is most common in individuals of Asian descent. The incidence across all types of EBT is estimated at 0.25% to 6% in the general population.²

Observed clinical variations of EBT range from simple polythelia (additional nipple[s] without associated parenchyma) to complete polymastia (organized and differentiated accessory breasts). Some types of EBT are rarer than others: One report of gynecologic cancer screenings in 1660 patients found polymastia and polythelia incidences of 0.12% and 5.48%, respectively.³ Of the symptomatic variations, isolated parenchymal EBT without a nipple or areolar complex is the most common and may manifest clinically as unilateral or bilateral tender, mildly erythematous nodules or masses often located in the axillae. Ectopic breast tissue generally is observed along the milk line, a developmental regional designation corresponding to the embryologic mammary ridge and extending linearly from the anterior axilla to the inguinal fold on both sides of the body; however, there have been rare reports of EBT manifesting in areas outside the milk line, such as the face, neck, back, vulva, and extremities.^2,3

Given that the underlying elements of EBT usually are hormone responsive (as with normal breast tissue), the initial symptom onset and subsequent manifestation frequently coincide with pubertal milestones, pregnancy, or lactation. Furthermore, some patients with EBT may experience symptom fluctuations in concordance with monthly menstrual phases. Many cases of EBT are selflimited and resolve within weeks to months after the end of a pregnancy or lactation, but some cases may persist. Continued observation and follow-up are advisable in all patients, as EBT symptoms often recur and the tissue is susceptible to the same disease processes that affect normal breasts, the most concerning of which is malignancy.⁴ Although the true incidence is limited by available data, primary ectopic breast malignancy has been estimated to account for 0.3% to 3.8% of diagnosed breast malignancies.² Cases of malignancy arising from EBT often are of higher grade and poorer prognosis, a finding that may be attributable to diagnostic delays caused by oversight or misdiagnosis of EBT rather than inherent differences in the biologic profile of the tumors.^2,4 Patients with a documented history of EBT may benefit from having their routine breast cancer screenings expanded to include areas with EBT foci.

Potential misdiagnoses for EBT include subcutaneous lipoma, axillary lymphadenopathy, abscess, hidradenitis suppurativa, or malignancy. Features that are suggestive of EBT include symptom association with hormone fluctuations (eg, menstrual phases), absence of fever, and lactescent rather than purulent drainage. Among reported EBT cases, spontaneous lactation rarely is described and, if present, often is associated with a history of prior trauma (eg, core needle biopsy or local abscess formation).⁵ This trauma creates an aberrant connection known as a milk fistula between the underlying parenchyma and the skin surface. Interestingly, our patient denied any history of axillary trauma, but she was noted to be lactating from an apparent milk fistula rather than an organized secretory duct system.

Though a patient history and clinical examination may be sufficient to diagnose EBT cases that are more physically apparent and well correlated with hormone fluctuations, many cases require additional diagnostic studies for confirmation. Of the tools available, ultrasonography generally is considered first-line due to its noninvasive nature, low cost, minimal risk, and high diagnostic value.² Ultrasonography quickly differentiates between abscesses and cystlike processes, which may appear as discrete areas of decreased echogenicity, and breast tissue, which manifests with fibroglandular tissue and lobules of fat.^2,6 Additionally, ultrasonography may demonstrate the secretion of milk through ducts or fistulae, if present. Should examination with ultrasonography prove inconclusive, follow-up studies using conventional radiographic mammography or magnetic resonance imaging may be warranted. Biopsy of EBT foci generally is not indicated unless first-line noninvasive studies fail to yield a conclusive diagnosis; however, biopsy also may be warranted if initial imaging is suggestive of malignancy arising from EBT.²

Management of EBT generally is conservative, and symptoms often resolve without intervention.⁴ Symptomatic relief may be achieved through techniques such as application of warm/cold compresses, avoidance of mechanical stimulation, and use of over-the-counter pain medicine. In cases that are persistent, frequently recurrent, or associated with severe symptoms or that cause considerable cosmetic impact, management with surgical excision and/or liposuction may be warranted.⁷ In our patient, the symptoms were not bothersome enough to warrant surgical intervention, so she was managed conservatively and did not return for follow-up.

THE DIAGNOSIS: Ectopic (Accessory) Breast Tissue

Ectopic (accessory) breast tissue (EBT) is a phenomenon caused by failed regression of one or more components of the embryonic mammary ridges— paired ectodermal thickenings that eventually develop into definitive breast tissue including the nipples, areolae, and parenchyma. Ectopic breast tissue is more common in women than men and is believed to be sporadic, although an autosomal-dominant inheritance mechanism with incomplete penetrance has been proposed for some cases.¹ The reported incidence of EBT varies greatly among racial and ethnic groups but is most common in individuals of Asian descent. The incidence across all types of EBT is estimated at 0.25% to 6% in the general population.²

Observed clinical variations of EBT range from simple polythelia (additional nipple[s] without associated parenchyma) to complete polymastia (organized and differentiated accessory breasts). Some types of EBT are rarer than others: One report of gynecologic cancer screenings in 1660 patients found polymastia and polythelia incidences of 0.12% and 5.48%, respectively.³ Of the symptomatic variations, isolated parenchymal EBT without a nipple or areolar complex is the most common and may manifest clinically as unilateral or bilateral tender, mildly erythematous nodules or masses often located in the axillae. Ectopic breast tissue generally is observed along the milk line, a developmental regional designation corresponding to the embryologic mammary ridge and extending linearly from the anterior axilla to the inguinal fold on both sides of the body; however, there have been rare reports of EBT manifesting in areas outside the milk line, such as the face, neck, back, vulva, and extremities.^2,3

Given that the underlying elements of EBT usually are hormone responsive (as with normal breast tissue), the initial symptom onset and subsequent manifestation frequently coincide with pubertal milestones, pregnancy, or lactation. Furthermore, some patients with EBT may experience symptom fluctuations in concordance with monthly menstrual phases. Many cases of EBT are selflimited and resolve within weeks to months after the end of a pregnancy or lactation, but some cases may persist. Continued observation and follow-up are advisable in all patients, as EBT symptoms often recur and the tissue is susceptible to the same disease processes that affect normal breasts, the most concerning of which is malignancy.⁴ Although the true incidence is limited by available data, primary ectopic breast malignancy has been estimated to account for 0.3% to 3.8% of diagnosed breast malignancies.² Cases of malignancy arising from EBT often are of higher grade and poorer prognosis, a finding that may be attributable to diagnostic delays caused by oversight or misdiagnosis of EBT rather than inherent differences in the biologic profile of the tumors.^2,4 Patients with a documented history of EBT may benefit from having their routine breast cancer screenings expanded to include areas with EBT foci.

Potential misdiagnoses for EBT include subcutaneous lipoma, axillary lymphadenopathy, abscess, hidradenitis suppurativa, or malignancy. Features that are suggestive of EBT include symptom association with hormone fluctuations (eg, menstrual phases), absence of fever, and lactescent rather than purulent drainage. Among reported EBT cases, spontaneous lactation rarely is described and, if present, often is associated with a history of prior trauma (eg, core needle biopsy or local abscess formation).⁵ This trauma creates an aberrant connection known as a milk fistula between the underlying parenchyma and the skin surface. Interestingly, our patient denied any history of axillary trauma, but she was noted to be lactating from an apparent milk fistula rather than an organized secretory duct system.

Though a patient history and clinical examination may be sufficient to diagnose EBT cases that are more physically apparent and well correlated with hormone fluctuations, many cases require additional diagnostic studies for confirmation. Of the tools available, ultrasonography generally is considered first-line due to its noninvasive nature, low cost, minimal risk, and high diagnostic value.² Ultrasonography quickly differentiates between abscesses and cystlike processes, which may appear as discrete areas of decreased echogenicity, and breast tissue, which manifests with fibroglandular tissue and lobules of fat.^2,6 Additionally, ultrasonography may demonstrate the secretion of milk through ducts or fistulae, if present. Should examination with ultrasonography prove inconclusive, follow-up studies using conventional radiographic mammography or magnetic resonance imaging may be warranted. Biopsy of EBT foci generally is not indicated unless first-line noninvasive studies fail to yield a conclusive diagnosis; however, biopsy also may be warranted if initial imaging is suggestive of malignancy arising from EBT.²

Management of EBT generally is conservative, and symptoms often resolve without intervention.⁴ Symptomatic relief may be achieved through techniques such as application of warm/cold compresses, avoidance of mechanical stimulation, and use of over-the-counter pain medicine. In cases that are persistent, frequently recurrent, or associated with severe symptoms or that cause considerable cosmetic impact, management with surgical excision and/or liposuction may be warranted.⁷ In our patient, the symptoms were not bothersome enough to warrant surgical intervention, so she was managed conservatively and did not return for follow-up.

The Diagnosis: Nevus Sebaceus of Jadassohn

The diagnosis of nevus sebaceus of Jadassohn was made clinically based on the lesion’s appearance and presence since birth as well as the absence of systemic symptoms. Clinically, nevus sebaceus of Jadassohn typically manifests as a well-demarcated, yellow- brown plaque often located on the scalp, as was seen in our patient. The lack of pruritus and pain further supported the diagnosis in our patient. No biopsy was performed, as the presentation was considered classic for this condition. Our patient opted to forgo surgery and will be routinely monitored for any changes, as nevus sebaceus has a potential risk, albeit low, for malignant transformation later in life. No changes have been observed since the initial presentation, and regular follow-ups are planned to monitor for future developments.

Nevus sebaceus of Jadassohn is a hamartomatous lesion involving the pilosebaceous follicle and adjacent adnexal structures.^1-3 It most commonly forms on the scalp (59.3%) and is accompanied by partial or total alopecia. ^3,4 It is seen less often on the face, periauricular area, or neck^1,4; thorax or limbs⁵; and oral or genital mucosae.⁶ Nevus sebaceus of Jadassohn affects approximately 0.3% of newborns,¹ usually as a solitary lesion that can form an extensive plaque. The male-to-female occurrence ratio has been reported as equal to slightly more predominant in females; all races and ethnicities are affected.^1,5

Nevus sebaceus of Jadassohn follows 3 stages of clinical development: infantile, adolescent, and adulthood. It manifests at birth or shortly afterward as a smooth hairless patch or plaque that is yellowish and can be hyperpigmented in Black patients.⁵ It may have an oval or linear configuration, typically is asymptomatic, and often arises along the Blaschko lines when it occurs as multiple lesions (a rare manifestation).¹ During puberty, hormonal changes cause accelerated growth, sebaceous gland maturation, and epidermal hyperplasia. ⁷ Nevus sebaceus of Jadassohn often is not identified until this stage, when its classic wartlike appearance has fully developed.¹

Patients with nevus sebaceus of Jadassohn have a 10% to 20% risk for tumor development in adulthood.^2,7 Trichoblastoma and syringocystadenoma papilliferum are the most frequently described neoplasms.⁸ Basal cell carcinoma is the most common malignant secondary neoplasm with an occurrence rate of 0.8%.^6,9 However, basal cell carcinoma and trichoblastoma may share histopathologic features, which may lead to misdiagnosis and a higher reported incidence of basal cell carcinoma in adults than is accurate.²

Early prophylactic surgical removal of nevus sebaceus of Jadassohn has been recommended; however, surgical management is controversial because the risk for a benign secondary neoplasm remains relatively high while the risk for malignancy is much lower.^2,7 Surgical excision remains an acceptable option once the patient is mature enough to tolerate the procedure.¹ However, patient education regarding watchful waiting vs a surgical approach— and the risks of each—is critical to ensure shared decision-making and a management plan tailored to the individual.

The differential diagnosis includes hypertrophic lichen planus, Langerhans cell histiocytosis (Letterer-Siwe disease type), epidermal nevus, and seborrheic keratosis. Hypertrophic lichen planus often occurs symmetrically on the dorsal feet and shins with thick, scaly, and extremely pruritic plaques. The lesions often persist for an average of 6 years and may lead to multiple keratoacanthomas or follicular base squamous cell carcinomas. Langerhans cell histiocytosis (Letterer-Siwe disease type) manifests with acute, disseminated, visceral, and cutaneous lesions before 2 years of age. These lesions appear as 1- to 2-mm, pink, seborrheic papules, pustules, or vesicles on the scalp, flexural neck, axilla, perineum, and trunk; they often are associated with petechiae, purpura, scale, crust, erosion, impetiginization, and tender fissures. Epidermal nevus occurs within the first year of life and is a hamartoma of the epidermis and papillary dermis. It manifests as papillomatous pigmented linear lines along the Blaschko lines. Seborrheic keratosis manifests as well-demarcated, waxy/verrucous, brown papules with a “stuck on” appearance on hair-bearing skin sparing the mucosae. They are common benign lesions associated with sun exposure and often manifest in the fourth decade of life.¹⁰

The Diagnosis: Nevus Sebaceus of Jadassohn

The diagnosis of nevus sebaceus of Jadassohn was made clinically based on the lesion’s appearance and presence since birth as well as the absence of systemic symptoms. Clinically, nevus sebaceus of Jadassohn typically manifests as a well-demarcated, yellow- brown plaque often located on the scalp, as was seen in our patient. The lack of pruritus and pain further supported the diagnosis in our patient. No biopsy was performed, as the presentation was considered classic for this condition. Our patient opted to forgo surgery and will be routinely monitored for any changes, as nevus sebaceus has a potential risk, albeit low, for malignant transformation later in life. No changes have been observed since the initial presentation, and regular follow-ups are planned to monitor for future developments.

Nevus sebaceus of Jadassohn is a hamartomatous lesion involving the pilosebaceous follicle and adjacent adnexal structures.^1-3 It most commonly forms on the scalp (59.3%) and is accompanied by partial or total alopecia. ^3,4 It is seen less often on the face, periauricular area, or neck^1,4; thorax or limbs⁵; and oral or genital mucosae.⁶ Nevus sebaceus of Jadassohn affects approximately 0.3% of newborns,¹ usually as a solitary lesion that can form an extensive plaque. The male-to-female occurrence ratio has been reported as equal to slightly more predominant in females; all races and ethnicities are affected.^1,5

Nevus sebaceus of Jadassohn follows 3 stages of clinical development: infantile, adolescent, and adulthood. It manifests at birth or shortly afterward as a smooth hairless patch or plaque that is yellowish and can be hyperpigmented in Black patients.⁵ It may have an oval or linear configuration, typically is asymptomatic, and often arises along the Blaschko lines when it occurs as multiple lesions (a rare manifestation).¹ During puberty, hormonal changes cause accelerated growth, sebaceous gland maturation, and epidermal hyperplasia. ⁷ Nevus sebaceus of Jadassohn often is not identified until this stage, when its classic wartlike appearance has fully developed.¹

Patients with nevus sebaceus of Jadassohn have a 10% to 20% risk for tumor development in adulthood.^2,7 Trichoblastoma and syringocystadenoma papilliferum are the most frequently described neoplasms.⁸ Basal cell carcinoma is the most common malignant secondary neoplasm with an occurrence rate of 0.8%.^6,9 However, basal cell carcinoma and trichoblastoma may share histopathologic features, which may lead to misdiagnosis and a higher reported incidence of basal cell carcinoma in adults than is accurate.²

Early prophylactic surgical removal of nevus sebaceus of Jadassohn has been recommended; however, surgical management is controversial because the risk for a benign secondary neoplasm remains relatively high while the risk for malignancy is much lower.^2,7 Surgical excision remains an acceptable option once the patient is mature enough to tolerate the procedure.¹ However, patient education regarding watchful waiting vs a surgical approach— and the risks of each—is critical to ensure shared decision-making and a management plan tailored to the individual.

The differential diagnosis includes hypertrophic lichen planus, Langerhans cell histiocytosis (Letterer-Siwe disease type), epidermal nevus, and seborrheic keratosis. Hypertrophic lichen planus often occurs symmetrically on the dorsal feet and shins with thick, scaly, and extremely pruritic plaques. The lesions often persist for an average of 6 years and may lead to multiple keratoacanthomas or follicular base squamous cell carcinomas. Langerhans cell histiocytosis (Letterer-Siwe disease type) manifests with acute, disseminated, visceral, and cutaneous lesions before 2 years of age. These lesions appear as 1- to 2-mm, pink, seborrheic papules, pustules, or vesicles on the scalp, flexural neck, axilla, perineum, and trunk; they often are associated with petechiae, purpura, scale, crust, erosion, impetiginization, and tender fissures. Epidermal nevus occurs within the first year of life and is a hamartoma of the epidermis and papillary dermis. It manifests as papillomatous pigmented linear lines along the Blaschko lines. Seborrheic keratosis manifests as well-demarcated, waxy/verrucous, brown papules with a “stuck on” appearance on hair-bearing skin sparing the mucosae. They are common benign lesions associated with sun exposure and often manifest in the fourth decade of life.¹⁰

The Diagnosis: Nevus Sebaceus of Jadassohn

The diagnosis of nevus sebaceus of Jadassohn was made clinically based on the lesion’s appearance and presence since birth as well as the absence of systemic symptoms. Clinically, nevus sebaceus of Jadassohn typically manifests as a well-demarcated, yellow- brown plaque often located on the scalp, as was seen in our patient. The lack of pruritus and pain further supported the diagnosis in our patient. No biopsy was performed, as the presentation was considered classic for this condition. Our patient opted to forgo surgery and will be routinely monitored for any changes, as nevus sebaceus has a potential risk, albeit low, for malignant transformation later in life. No changes have been observed since the initial presentation, and regular follow-ups are planned to monitor for future developments.

Nevus sebaceus of Jadassohn is a hamartomatous lesion involving the pilosebaceous follicle and adjacent adnexal structures.^1-3 It most commonly forms on the scalp (59.3%) and is accompanied by partial or total alopecia. ^3,4 It is seen less often on the face, periauricular area, or neck^1,4; thorax or limbs⁵; and oral or genital mucosae.⁶ Nevus sebaceus of Jadassohn affects approximately 0.3% of newborns,¹ usually as a solitary lesion that can form an extensive plaque. The male-to-female occurrence ratio has been reported as equal to slightly more predominant in females; all races and ethnicities are affected.^1,5

Nevus sebaceus of Jadassohn follows 3 stages of clinical development: infantile, adolescent, and adulthood. It manifests at birth or shortly afterward as a smooth hairless patch or plaque that is yellowish and can be hyperpigmented in Black patients.⁵ It may have an oval or linear configuration, typically is asymptomatic, and often arises along the Blaschko lines when it occurs as multiple lesions (a rare manifestation).¹ During puberty, hormonal changes cause accelerated growth, sebaceous gland maturation, and epidermal hyperplasia. ⁷ Nevus sebaceus of Jadassohn often is not identified until this stage, when its classic wartlike appearance has fully developed.¹

Patients with nevus sebaceus of Jadassohn have a 10% to 20% risk for tumor development in adulthood.^2,7 Trichoblastoma and syringocystadenoma papilliferum are the most frequently described neoplasms.⁸ Basal cell carcinoma is the most common malignant secondary neoplasm with an occurrence rate of 0.8%.^6,9 However, basal cell carcinoma and trichoblastoma may share histopathologic features, which may lead to misdiagnosis and a higher reported incidence of basal cell carcinoma in adults than is accurate.²

Early prophylactic surgical removal of nevus sebaceus of Jadassohn has been recommended; however, surgical management is controversial because the risk for a benign secondary neoplasm remains relatively high while the risk for malignancy is much lower.^2,7 Surgical excision remains an acceptable option once the patient is mature enough to tolerate the procedure.¹ However, patient education regarding watchful waiting vs a surgical approach— and the risks of each—is critical to ensure shared decision-making and a management plan tailored to the individual.

The differential diagnosis includes hypertrophic lichen planus, Langerhans cell histiocytosis (Letterer-Siwe disease type), epidermal nevus, and seborrheic keratosis. Hypertrophic lichen planus often occurs symmetrically on the dorsal feet and shins with thick, scaly, and extremely pruritic plaques. The lesions often persist for an average of 6 years and may lead to multiple keratoacanthomas or follicular base squamous cell carcinomas. Langerhans cell histiocytosis (Letterer-Siwe disease type) manifests with acute, disseminated, visceral, and cutaneous lesions before 2 years of age. These lesions appear as 1- to 2-mm, pink, seborrheic papules, pustules, or vesicles on the scalp, flexural neck, axilla, perineum, and trunk; they often are associated with petechiae, purpura, scale, crust, erosion, impetiginization, and tender fissures. Epidermal nevus occurs within the first year of life and is a hamartoma of the epidermis and papillary dermis. It manifests as papillomatous pigmented linear lines along the Blaschko lines. Seborrheic keratosis manifests as well-demarcated, waxy/verrucous, brown papules with a “stuck on” appearance on hair-bearing skin sparing the mucosae. They are common benign lesions associated with sun exposure and often manifest in the fourth decade of life.¹⁰

THE DIAGNOSIS: Dengue Hemorrhagic Fever

The retiform purpura observed in our patient was suggestive of a vasculitic, thrombotic, or embolic etiology. Dengue IgM serologic testing performed based on her extensive travel history and recent return from a dengue-endemic area was positive, indicating acute infection. A clinical diagnosis of dengue hemorrhagic fever (DHF) was made based on the hemorrhagic appearance of the lesion. Histopathology revealed leukocytoclastic vasculitis (Figure). Anti–double-stranded DNA, antideoxyribonuclease, C3 and C4, CH50 (total hemolytic complement), antineutrophil cytoplasmic antibodies, HIV, and hepatitis B virus tests were normal. Direct immunofluorescence was negative.

Dengue virus is a single-stranded RNA virus transmitted by Aedes aegypti and Aedes albopictus mosquitoes and is one of the most prevalent arthropod-borne viruses affecting humans today.^1,2 Infection with the dengue virus generally is seen in travelers visiting tropical regions of Africa, Mexico, South America, South and Central Asia, Southeast Asia, and the Caribbean.¹ The Table shows the global distribution of dengue serotypes from 2000 to 2014.^3,4 There are 4 serotypes of the dengue virus: DENV-1 to DENV-4. Infection with 1 strain elicits longlasting immunity to that strain, but subsequent infection with another strain can result in severe DHF due to antibody cross-reaction.¹

Dengue virus infection ranges from mildly symptomatic to a spectrum of increasingly severe conditions that comprise dengue fever (DF) and DHF, as well as dengue shock syndrome and brain stem hemorrhage, which may be fatal.^2,5 Dengue fever manifests as severe myalgia, fever, headache (usually retro-orbital), arthralgia, erythema, and rubelliform exanthema.⁶ The frequency of skin eruptions in patients with DF varies with the virus strain and outbreaks.⁷ The lesions initially develop with the onset of fever and manifest as flushing or erythematous mottling of the face, neck, and chest areas.^1,7 The morbilliform eruption develops 2 to 6 days after the onset of the fever, beginning on the trunk and spreading to the face and extremities.^1,7 The rash may become confluent with characteristic sparing of small round areas of normal skin described as white islands in a sea of red.² Verrucous papules on the ears also have been described and may resemble those seen in Cowden syndrome. In patients with prior infection with a different strain of the virus, hemorrhagic lesions may develop, including characteristic retiform purpura, a positive tourniquet test, and the appearance of petechiae on the lower legs. Pruritus and desquamation, especially on the palms and soles, may follow the termination of the eruption.⁷

The differential diagnosis of DF includes measles, rubella, enteroviruses, and influenza. Chikungunya and West Nile viruses in Asia and Africa and the O’nyong-nyong virus in Africa are also arboviruses that cause a clinical picture similar to DF but not DHF. Other diagnostic considerations include phases of scarlet fever, typhoid, malaria, leptospirosis, hepatitis A, and trypanosomal and rickettsial diseases.⁷ The differential diagnosis of DHF includes antineutrophil cytoplasmic antibody–associated vasculitis, rheumatoid vasculitis, and bacterial septic vasculitis.

Acute clinical diagnosis of DF can be challenging because of the nonspecific symptoms that can be seen in almost every infectious disease. Clinical presentation assessment should be confirmed with laboratory testing.⁶ Dengue virus infection usually is confirmed by the identification of viral genomic RNA, antigens, or the antibodies it elicits. Enzyme-linked immunosorbent assay–based serologic tests are cost-effective and easy to perform.⁵ IgM antibodies usually show cross-reactivity with platelets, but the antibody levels are not positively correlated with the severity of DF.⁸ Primary infection with the dengue virus is characterized by the elevation of specific IgM levels that usually occurs 3 to 5 days after symptom onset and persists during the postfebrile stage (up to 30 to 60 days). In secondary infections, the IgM levels usually rise more slowly and reach a lower level than in primary infections.⁹ For both primary and secondary infections, testing IgM levels after the febrile stage may be helpful with the laboratory diagnosis.

Currently, there is no antiviral drug available for dengue. Treatment of dengue infection is symptomatic and supportive.²

Dengue hemorrhagic fever is indicated by a rising hematocrit (≥20%) and a falling platelet count (>100,000/mm³) accompanying clinical signs of hemorrhage. Treatment includes intravenous fluid replacement and careful clinical monitoring of hematocrit levels, platelet count, vitals, urine output, and other signs of shock.⁵ For patients with a history of dengue infection, travel to areas with other serotypes is not recommended.

If any travel to a high-risk area is planned, countryspecific travel recommendations and warnings should be reviewed from the Centers for Disease Control and Prevention’s website (https://wwwnc.cdc.gov/travel/notices/level1/dengue-global). Use of an Environmental Protection Agency–registered insect repellent to avoid mosquito bites and acetaminophen for managing symptoms is advised. During travel, staying in places with window and door screens and using a bed net during sleep are suggested. Long-sleeved shirts and long pants also are preferred. Travelers should see a health care provider if they have symptoms of dengue.¹⁰

African tick bite fever (ATBF) is caused by Rickettsia africae transmitted by Amblyomma ticks. Skin findings in ATBF include erythematous, firm, tender papules with central eschars consistent with the feeding patterns of ticks.¹¹ Histopathology of ATBF usually includes fibrinoid necrosis of vessels in the dermis with a perivascular inflammatory infiltrate and coagulation necrosis of the surrounding dermis consistent with eschar formation.¹² The lack of an eschar weighs against this diagnosis.

African trypanosomiasis (also known as sleeping sickness) is caused by protozoa transmitted by the tsetse fly. A chancrelike, circumscribed, rubbery, indurated red or violaceous nodule measuring 2 to 5 cm in diameter often develops as the earliest cutaneous sign of the disease.¹³ Nonspecific histopathologic findings, such as infiltration of lymphocytes and macrophages and proliferation of endothelial cells and fibroblasts, may be observed.¹⁴ Extravascular parasites have been noted in skin biopsies.¹⁵ In later stages, skin lesions called trypanids may be observed as macular, papular, annular, targetoid, purpuric, and erythematous lesions, and histopathologic findings consistent with vasculitis also may be seen.¹³

Chikungunya virus infection is an acute-onset, mosquito-borne viral disease. Skin manifestations may start with nonspecific, generalized, morbilliform, maculopapular rashes coinciding with fever, which also may be seen initially with DHF. Skin hyperpigmentation, mostly centrofacial and involving the nose (chik sign); purpuric and ecchymotic lesions over the trunk and flexors of limbs in adults, often surmounted by subepidermal bullae and lesions resembling toxic epidermal necrolysis; and nonhealing ulcers in the genital and groin areas are common skin manifestations of chikungunya infection.¹⁶ Intraepithelial splitting with acantholysis and perivascular lymphohistiocytic infiltration may be observed in the histopathology of blistering lesions, which are not consistent with DHF.¹⁷

Zika virus infection is caused by an arbovirus within the Flaviviridae family, which also includes the dengue virus. Initial mucocutaneous findings of the Zika virus include nonspecific diffuse maculopapular eruptions. The eruption generally spares the palms and soles; however, various manifestations including involvement of the palms and soles have been reported.¹⁸ The morbilliform eruption begins on the face and extends to the trunk and extremities. Mild hemorrhagic manifestations, including petechiae and bleeding gums, may be observed. Distinguishing between dengue and Zika virus infection relies on the severity of symptoms and laboratory tests, including polymerase chain reaction or IgM antibody testing.¹⁹ The other conditions listed do not produce hemorrhagic fever.

THE DIAGNOSIS: Dengue Hemorrhagic Fever

The retiform purpura observed in our patient was suggestive of a vasculitic, thrombotic, or embolic etiology. Dengue IgM serologic testing performed based on her extensive travel history and recent return from a dengue-endemic area was positive, indicating acute infection. A clinical diagnosis of dengue hemorrhagic fever (DHF) was made based on the hemorrhagic appearance of the lesion. Histopathology revealed leukocytoclastic vasculitis (Figure). Anti–double-stranded DNA, antideoxyribonuclease, C3 and C4, CH50 (total hemolytic complement), antineutrophil cytoplasmic antibodies, HIV, and hepatitis B virus tests were normal. Direct immunofluorescence was negative.

Dengue virus is a single-stranded RNA virus transmitted by Aedes aegypti and Aedes albopictus mosquitoes and is one of the most prevalent arthropod-borne viruses affecting humans today.^1,2 Infection with the dengue virus generally is seen in travelers visiting tropical regions of Africa, Mexico, South America, South and Central Asia, Southeast Asia, and the Caribbean.¹ The Table shows the global distribution of dengue serotypes from 2000 to 2014.^3,4 There are 4 serotypes of the dengue virus: DENV-1 to DENV-4. Infection with 1 strain elicits longlasting immunity to that strain, but subsequent infection with another strain can result in severe DHF due to antibody cross-reaction.¹

Dengue virus infection ranges from mildly symptomatic to a spectrum of increasingly severe conditions that comprise dengue fever (DF) and DHF, as well as dengue shock syndrome and brain stem hemorrhage, which may be fatal.^2,5 Dengue fever manifests as severe myalgia, fever, headache (usually retro-orbital), arthralgia, erythema, and rubelliform exanthema.⁶ The frequency of skin eruptions in patients with DF varies with the virus strain and outbreaks.⁷ The lesions initially develop with the onset of fever and manifest as flushing or erythematous mottling of the face, neck, and chest areas.^1,7 The morbilliform eruption develops 2 to 6 days after the onset of the fever, beginning on the trunk and spreading to the face and extremities.^1,7 The rash may become confluent with characteristic sparing of small round areas of normal skin described as white islands in a sea of red.² Verrucous papules on the ears also have been described and may resemble those seen in Cowden syndrome. In patients with prior infection with a different strain of the virus, hemorrhagic lesions may develop, including characteristic retiform purpura, a positive tourniquet test, and the appearance of petechiae on the lower legs. Pruritus and desquamation, especially on the palms and soles, may follow the termination of the eruption.⁷

The differential diagnosis of DF includes measles, rubella, enteroviruses, and influenza. Chikungunya and West Nile viruses in Asia and Africa and the O’nyong-nyong virus in Africa are also arboviruses that cause a clinical picture similar to DF but not DHF. Other diagnostic considerations include phases of scarlet fever, typhoid, malaria, leptospirosis, hepatitis A, and trypanosomal and rickettsial diseases.⁷ The differential diagnosis of DHF includes antineutrophil cytoplasmic antibody–associated vasculitis, rheumatoid vasculitis, and bacterial septic vasculitis.

Acute clinical diagnosis of DF can be challenging because of the nonspecific symptoms that can be seen in almost every infectious disease. Clinical presentation assessment should be confirmed with laboratory testing.⁶ Dengue virus infection usually is confirmed by the identification of viral genomic RNA, antigens, or the antibodies it elicits. Enzyme-linked immunosorbent assay–based serologic tests are cost-effective and easy to perform.⁵ IgM antibodies usually show cross-reactivity with platelets, but the antibody levels are not positively correlated with the severity of DF.⁸ Primary infection with the dengue virus is characterized by the elevation of specific IgM levels that usually occurs 3 to 5 days after symptom onset and persists during the postfebrile stage (up to 30 to 60 days). In secondary infections, the IgM levels usually rise more slowly and reach a lower level than in primary infections.⁹ For both primary and secondary infections, testing IgM levels after the febrile stage may be helpful with the laboratory diagnosis.

Currently, there is no antiviral drug available for dengue. Treatment of dengue infection is symptomatic and supportive.²

Dengue hemorrhagic fever is indicated by a rising hematocrit (≥20%) and a falling platelet count (>100,000/mm³) accompanying clinical signs of hemorrhage. Treatment includes intravenous fluid replacement and careful clinical monitoring of hematocrit levels, platelet count, vitals, urine output, and other signs of shock.⁵ For patients with a history of dengue infection, travel to areas with other serotypes is not recommended.

If any travel to a high-risk area is planned, countryspecific travel recommendations and warnings should be reviewed from the Centers for Disease Control and Prevention’s website (https://wwwnc.cdc.gov/travel/notices/level1/dengue-global). Use of an Environmental Protection Agency–registered insect repellent to avoid mosquito bites and acetaminophen for managing symptoms is advised. During travel, staying in places with window and door screens and using a bed net during sleep are suggested. Long-sleeved shirts and long pants also are preferred. Travelers should see a health care provider if they have symptoms of dengue.¹⁰

African tick bite fever (ATBF) is caused by Rickettsia africae transmitted by Amblyomma ticks. Skin findings in ATBF include erythematous, firm, tender papules with central eschars consistent with the feeding patterns of ticks.¹¹ Histopathology of ATBF usually includes fibrinoid necrosis of vessels in the dermis with a perivascular inflammatory infiltrate and coagulation necrosis of the surrounding dermis consistent with eschar formation.¹² The lack of an eschar weighs against this diagnosis.

African trypanosomiasis (also known as sleeping sickness) is caused by protozoa transmitted by the tsetse fly. A chancrelike, circumscribed, rubbery, indurated red or violaceous nodule measuring 2 to 5 cm in diameter often develops as the earliest cutaneous sign of the disease.¹³ Nonspecific histopathologic findings, such as infiltration of lymphocytes and macrophages and proliferation of endothelial cells and fibroblasts, may be observed.¹⁴ Extravascular parasites have been noted in skin biopsies.¹⁵ In later stages, skin lesions called trypanids may be observed as macular, papular, annular, targetoid, purpuric, and erythematous lesions, and histopathologic findings consistent with vasculitis also may be seen.¹³

Chikungunya virus infection is an acute-onset, mosquito-borne viral disease. Skin manifestations may start with nonspecific, generalized, morbilliform, maculopapular rashes coinciding with fever, which also may be seen initially with DHF. Skin hyperpigmentation, mostly centrofacial and involving the nose (chik sign); purpuric and ecchymotic lesions over the trunk and flexors of limbs in adults, often surmounted by subepidermal bullae and lesions resembling toxic epidermal necrolysis; and nonhealing ulcers in the genital and groin areas are common skin manifestations of chikungunya infection.¹⁶ Intraepithelial splitting with acantholysis and perivascular lymphohistiocytic infiltration may be observed in the histopathology of blistering lesions, which are not consistent with DHF.¹⁷

Zika virus infection is caused by an arbovirus within the Flaviviridae family, which also includes the dengue virus. Initial mucocutaneous findings of the Zika virus include nonspecific diffuse maculopapular eruptions. The eruption generally spares the palms and soles; however, various manifestations including involvement of the palms and soles have been reported.¹⁸ The morbilliform eruption begins on the face and extends to the trunk and extremities. Mild hemorrhagic manifestations, including petechiae and bleeding gums, may be observed. Distinguishing between dengue and Zika virus infection relies on the severity of symptoms and laboratory tests, including polymerase chain reaction or IgM antibody testing.¹⁹ The other conditions listed do not produce hemorrhagic fever.

THE DIAGNOSIS: Dengue Hemorrhagic Fever

The retiform purpura observed in our patient was suggestive of a vasculitic, thrombotic, or embolic etiology. Dengue IgM serologic testing performed based on her extensive travel history and recent return from a dengue-endemic area was positive, indicating acute infection. A clinical diagnosis of dengue hemorrhagic fever (DHF) was made based on the hemorrhagic appearance of the lesion. Histopathology revealed leukocytoclastic vasculitis (Figure). Anti–double-stranded DNA, antideoxyribonuclease, C3 and C4, CH50 (total hemolytic complement), antineutrophil cytoplasmic antibodies, HIV, and hepatitis B virus tests were normal. Direct immunofluorescence was negative.

Dengue virus is a single-stranded RNA virus transmitted by Aedes aegypti and Aedes albopictus mosquitoes and is one of the most prevalent arthropod-borne viruses affecting humans today.^1,2 Infection with the dengue virus generally is seen in travelers visiting tropical regions of Africa, Mexico, South America, South and Central Asia, Southeast Asia, and the Caribbean.¹ The Table shows the global distribution of dengue serotypes from 2000 to 2014.^3,4 There are 4 serotypes of the dengue virus: DENV-1 to DENV-4. Infection with 1 strain elicits longlasting immunity to that strain, but subsequent infection with another strain can result in severe DHF due to antibody cross-reaction.¹

Dengue virus infection ranges from mildly symptomatic to a spectrum of increasingly severe conditions that comprise dengue fever (DF) and DHF, as well as dengue shock syndrome and brain stem hemorrhage, which may be fatal.^2,5 Dengue fever manifests as severe myalgia, fever, headache (usually retro-orbital), arthralgia, erythema, and rubelliform exanthema.⁶ The frequency of skin eruptions in patients with DF varies with the virus strain and outbreaks.⁷ The lesions initially develop with the onset of fever and manifest as flushing or erythematous mottling of the face, neck, and chest areas.^1,7 The morbilliform eruption develops 2 to 6 days after the onset of the fever, beginning on the trunk and spreading to the face and extremities.^1,7 The rash may become confluent with characteristic sparing of small round areas of normal skin described as white islands in a sea of red.² Verrucous papules on the ears also have been described and may resemble those seen in Cowden syndrome. In patients with prior infection with a different strain of the virus, hemorrhagic lesions may develop, including characteristic retiform purpura, a positive tourniquet test, and the appearance of petechiae on the lower legs. Pruritus and desquamation, especially on the palms and soles, may follow the termination of the eruption.⁷

The differential diagnosis of DF includes measles, rubella, enteroviruses, and influenza. Chikungunya and West Nile viruses in Asia and Africa and the O’nyong-nyong virus in Africa are also arboviruses that cause a clinical picture similar to DF but not DHF. Other diagnostic considerations include phases of scarlet fever, typhoid, malaria, leptospirosis, hepatitis A, and trypanosomal and rickettsial diseases.⁷ The differential diagnosis of DHF includes antineutrophil cytoplasmic antibody–associated vasculitis, rheumatoid vasculitis, and bacterial septic vasculitis.

Acute clinical diagnosis of DF can be challenging because of the nonspecific symptoms that can be seen in almost every infectious disease. Clinical presentation assessment should be confirmed with laboratory testing.⁶ Dengue virus infection usually is confirmed by the identification of viral genomic RNA, antigens, or the antibodies it elicits. Enzyme-linked immunosorbent assay–based serologic tests are cost-effective and easy to perform.⁵ IgM antibodies usually show cross-reactivity with platelets, but the antibody levels are not positively correlated with the severity of DF.⁸ Primary infection with the dengue virus is characterized by the elevation of specific IgM levels that usually occurs 3 to 5 days after symptom onset and persists during the postfebrile stage (up to 30 to 60 days). In secondary infections, the IgM levels usually rise more slowly and reach a lower level than in primary infections.⁹ For both primary and secondary infections, testing IgM levels after the febrile stage may be helpful with the laboratory diagnosis.

Currently, there is no antiviral drug available for dengue. Treatment of dengue infection is symptomatic and supportive.²

Dengue hemorrhagic fever is indicated by a rising hematocrit (≥20%) and a falling platelet count (>100,000/mm³) accompanying clinical signs of hemorrhage. Treatment includes intravenous fluid replacement and careful clinical monitoring of hematocrit levels, platelet count, vitals, urine output, and other signs of shock.⁵ For patients with a history of dengue infection, travel to areas with other serotypes is not recommended.

If any travel to a high-risk area is planned, countryspecific travel recommendations and warnings should be reviewed from the Centers for Disease Control and Prevention’s website (https://wwwnc.cdc.gov/travel/notices/level1/dengue-global). Use of an Environmental Protection Agency–registered insect repellent to avoid mosquito bites and acetaminophen for managing symptoms is advised. During travel, staying in places with window and door screens and using a bed net during sleep are suggested. Long-sleeved shirts and long pants also are preferred. Travelers should see a health care provider if they have symptoms of dengue.¹⁰

African tick bite fever (ATBF) is caused by Rickettsia africae transmitted by Amblyomma ticks. Skin findings in ATBF include erythematous, firm, tender papules with central eschars consistent with the feeding patterns of ticks.¹¹ Histopathology of ATBF usually includes fibrinoid necrosis of vessels in the dermis with a perivascular inflammatory infiltrate and coagulation necrosis of the surrounding dermis consistent with eschar formation.¹² The lack of an eschar weighs against this diagnosis.

African trypanosomiasis (also known as sleeping sickness) is caused by protozoa transmitted by the tsetse fly. A chancrelike, circumscribed, rubbery, indurated red or violaceous nodule measuring 2 to 5 cm in diameter often develops as the earliest cutaneous sign of the disease.¹³ Nonspecific histopathologic findings, such as infiltration of lymphocytes and macrophages and proliferation of endothelial cells and fibroblasts, may be observed.¹⁴ Extravascular parasites have been noted in skin biopsies.¹⁵ In later stages, skin lesions called trypanids may be observed as macular, papular, annular, targetoid, purpuric, and erythematous lesions, and histopathologic findings consistent with vasculitis also may be seen.¹³

Chikungunya virus infection is an acute-onset, mosquito-borne viral disease. Skin manifestations may start with nonspecific, generalized, morbilliform, maculopapular rashes coinciding with fever, which also may be seen initially with DHF. Skin hyperpigmentation, mostly centrofacial and involving the nose (chik sign); purpuric and ecchymotic lesions over the trunk and flexors of limbs in adults, often surmounted by subepidermal bullae and lesions resembling toxic epidermal necrolysis; and nonhealing ulcers in the genital and groin areas are common skin manifestations of chikungunya infection.¹⁶ Intraepithelial splitting with acantholysis and perivascular lymphohistiocytic infiltration may be observed in the histopathology of blistering lesions, which are not consistent with DHF.¹⁷

Zika virus infection is caused by an arbovirus within the Flaviviridae family, which also includes the dengue virus. Initial mucocutaneous findings of the Zika virus include nonspecific diffuse maculopapular eruptions. The eruption generally spares the palms and soles; however, various manifestations including involvement of the palms and soles have been reported.¹⁸ The morbilliform eruption begins on the face and extends to the trunk and extremities. Mild hemorrhagic manifestations, including petechiae and bleeding gums, may be observed. Distinguishing between dengue and Zika virus infection relies on the severity of symptoms and laboratory tests, including polymerase chain reaction or IgM antibody testing.¹⁹ The other conditions listed do not produce hemorrhagic fever.

THE DIAGNOSIS: Secondary Syphilis

Histopathology demonstrated a mild superficial perivascular and interstitial infiltrate composed of lymphocytes, histiocytes, and rare plasma cells with a background of extravasated erythrocytes (Figure, A). Treponema pallidum staining highlighted multiple spirochetes along the dermoepidermal junction and in the superficial dermis (Figure, B). Direct immunofluorescence was negative. Laboratory workup revealed a reactive rapid plasma reagin screen with a titer of 1:16 and positive IgG and IgM treponemal antibodies. The patient was diagnosed with secondary syphilis and was treated with a single dose of 2.4 million U of intramuscular benzathine penicillin G, with notable improvement of the rash and arthritis symptoms at 2-week follow-up.

Syphilis is a sexually transmitted infection caused by the spirochete T pallidum that progresses through active and latent stages. The incidence of both the primary and secondary stages of syphilis was at a historic low in the year 2000 and has increased annually since then.¹ Syphilis is more common in men, and men who have sex with men (MSM) are disproportionately affected. Although the incidence of syphilis in MSM has increased since 2000, rates have slowed, with slight decreases in this population between 2019 and 2020.¹ Conversely, rates among women have increased substantially in recent years, suggesting a more recent epidemic affecting heterosexual men and women.²

Classically, the primary stage of syphilis manifests as an asymptomatic papule followed by a painless ulcer (chancre) that heals spontaneously. The secondary stage of syphilis results from dissemination of T pallidum and is characterized by a wide range of mucocutaneous manifestations and prodromal symptoms. The most common cutaneous manifestation is a diffuse, nonpruritic, papulosquamous rash with red-brown scaly macules or papules on the trunk and extremities.³ The palms and soles commonly are involved. Mucosal patches, “snail-track” ulcers in the mouth, and condylomata lata are the characteristic mucosal lesions of secondary syphilis. Mucocutaneous findings typically are preceded by systemic signs including fever, malaise, myalgia, and generalized lymphadenopathy. However, syphilis is considered “the great mimicker,” with new reports of unusual presentations of the disease. In addition to papulosquamous morphologies, pustular, targetoid, psoriasiform, and noduloulcerative (also known as lues maligna) forms of syphilis have been reported.^3-5

The histopathologic features of secondary syphilis also are variable. Classically, secondary syphilis demonstrates vacuolar interface dermatitis and acanthosis with slender elongated rete ridges. Other well-known features include endothelial swelling and the presence of plasma cells in most cases.⁶ However, the histopathologic features of secondary syphilis may vary depending on the morphology of the skin eruption and when the biopsy is taken. Our patient lacked the classic histopathologic features of secondary syphilis. However, because syphilis was in the clinical differential diagnosis, a treponemal stain was ordered and confirmed the diagnosis. Immunohistochemical stains using antibodies to treponemal antigens have a reported sensitivity of 71% to 100% and are highly specific.⁷ Although the combination of endothelial swelling, interstitial inflammation, irregular acanthosis, and elongated rete ridges should raise the possibility of syphilis, a treponemal stain may be useful to identify spirochetes if clinical suspicion exists.⁸

Given our patient’s known history of GPA, leukocytoclastic vasculitis was high on the list of differential diagnoses. However, leukocytoclastic vasculitis most classically manifests as petechiae and palpable purpura, and unlike in secondary syphilis, the palms and soles are less commonly involved. Because our patient’s rash was mainly localized to the lower limbs, the differential also included 2 pigmented purpuric dermatoses (PPDs): progressive pigmentary purpura (Schamberg disease) and purpura annularis telangiectodes (Majocchi disease). Progressive pigmentary purpura is the most common manifestation of PPD and appears as cayenne pepper–colored macules that coalesce into golden brown–pigmented patches on the legs.⁹ Purpura annularis telangiectodes is another variant of PPD that manifests as pinpoint telangiectatic macules that progress to annular hyperpigmented patches with central clearing. Although PPDs frequently occur on the lower extremities, reports of plantar involvement are rare.¹⁰ Annular lichen planus manifests as violaceous papules with a clear center; however, it would be atypical for these lesions to be restricted to the feet and ankles. Palmoplantar lichen planus can mimic secondary syphilis clinically, but these cases manifest as hyperkeratotic pruritic papules on the palms and soles in contrast to the faint brown asymptomatic macules noted in our case.¹¹

Our case highlights an unusual presentation of secondary syphilis and demonstrates the challenge of diagnosing this entity on clinical presentation alone. Because this patient lacked the classic clinical and histopathologic features of secondary syphilis, a skin biopsy with positive immunohistochemical staining for treponemal antigens was necessary to make the diagnosis. Given the variability in presentation of secondary syphilis, a biopsy or serologic testing may be necessary to make a proper diagnosis.

THE DIAGNOSIS: Secondary Syphilis

Histopathology demonstrated a mild superficial perivascular and interstitial infiltrate composed of lymphocytes, histiocytes, and rare plasma cells with a background of extravasated erythrocytes (Figure, A). Treponema pallidum staining highlighted multiple spirochetes along the dermoepidermal junction and in the superficial dermis (Figure, B). Direct immunofluorescence was negative. Laboratory workup revealed a reactive rapid plasma reagin screen with a titer of 1:16 and positive IgG and IgM treponemal antibodies. The patient was diagnosed with secondary syphilis and was treated with a single dose of 2.4 million U of intramuscular benzathine penicillin G, with notable improvement of the rash and arthritis symptoms at 2-week follow-up.

Syphilis is a sexually transmitted infection caused by the spirochete T pallidum that progresses through active and latent stages. The incidence of both the primary and secondary stages of syphilis was at a historic low in the year 2000 and has increased annually since then.¹ Syphilis is more common in men, and men who have sex with men (MSM) are disproportionately affected. Although the incidence of syphilis in MSM has increased since 2000, rates have slowed, with slight decreases in this population between 2019 and 2020.¹ Conversely, rates among women have increased substantially in recent years, suggesting a more recent epidemic affecting heterosexual men and women.²

Classically, the primary stage of syphilis manifests as an asymptomatic papule followed by a painless ulcer (chancre) that heals spontaneously. The secondary stage of syphilis results from dissemination of T pallidum and is characterized by a wide range of mucocutaneous manifestations and prodromal symptoms. The most common cutaneous manifestation is a diffuse, nonpruritic, papulosquamous rash with red-brown scaly macules or papules on the trunk and extremities.³ The palms and soles commonly are involved. Mucosal patches, “snail-track” ulcers in the mouth, and condylomata lata are the characteristic mucosal lesions of secondary syphilis. Mucocutaneous findings typically are preceded by systemic signs including fever, malaise, myalgia, and generalized lymphadenopathy. However, syphilis is considered “the great mimicker,” with new reports of unusual presentations of the disease. In addition to papulosquamous morphologies, pustular, targetoid, psoriasiform, and noduloulcerative (also known as lues maligna) forms of syphilis have been reported.^3-5

The histopathologic features of secondary syphilis also are variable. Classically, secondary syphilis demonstrates vacuolar interface dermatitis and acanthosis with slender elongated rete ridges. Other well-known features include endothelial swelling and the presence of plasma cells in most cases.⁶ However, the histopathologic features of secondary syphilis may vary depending on the morphology of the skin eruption and when the biopsy is taken. Our patient lacked the classic histopathologic features of secondary syphilis. However, because syphilis was in the clinical differential diagnosis, a treponemal stain was ordered and confirmed the diagnosis. Immunohistochemical stains using antibodies to treponemal antigens have a reported sensitivity of 71% to 100% and are highly specific.⁷ Although the combination of endothelial swelling, interstitial inflammation, irregular acanthosis, and elongated rete ridges should raise the possibility of syphilis, a treponemal stain may be useful to identify spirochetes if clinical suspicion exists.⁸

Given our patient’s known history of GPA, leukocytoclastic vasculitis was high on the list of differential diagnoses. However, leukocytoclastic vasculitis most classically manifests as petechiae and palpable purpura, and unlike in secondary syphilis, the palms and soles are less commonly involved. Because our patient’s rash was mainly localized to the lower limbs, the differential also included 2 pigmented purpuric dermatoses (PPDs): progressive pigmentary purpura (Schamberg disease) and purpura annularis telangiectodes (Majocchi disease). Progressive pigmentary purpura is the most common manifestation of PPD and appears as cayenne pepper–colored macules that coalesce into golden brown–pigmented patches on the legs.⁹ Purpura annularis telangiectodes is another variant of PPD that manifests as pinpoint telangiectatic macules that progress to annular hyperpigmented patches with central clearing. Although PPDs frequently occur on the lower extremities, reports of plantar involvement are rare.¹⁰ Annular lichen planus manifests as violaceous papules with a clear center; however, it would be atypical for these lesions to be restricted to the feet and ankles. Palmoplantar lichen planus can mimic secondary syphilis clinically, but these cases manifest as hyperkeratotic pruritic papules on the palms and soles in contrast to the faint brown asymptomatic macules noted in our case.¹¹

Our case highlights an unusual presentation of secondary syphilis and demonstrates the challenge of diagnosing this entity on clinical presentation alone. Because this patient lacked the classic clinical and histopathologic features of secondary syphilis, a skin biopsy with positive immunohistochemical staining for treponemal antigens was necessary to make the diagnosis. Given the variability in presentation of secondary syphilis, a biopsy or serologic testing may be necessary to make a proper diagnosis.

THE DIAGNOSIS: Secondary Syphilis

Histopathology demonstrated a mild superficial perivascular and interstitial infiltrate composed of lymphocytes, histiocytes, and rare plasma cells with a background of extravasated erythrocytes (Figure, A). Treponema pallidum staining highlighted multiple spirochetes along the dermoepidermal junction and in the superficial dermis (Figure, B). Direct immunofluorescence was negative. Laboratory workup revealed a reactive rapid plasma reagin screen with a titer of 1:16 and positive IgG and IgM treponemal antibodies. The patient was diagnosed with secondary syphilis and was treated with a single dose of 2.4 million U of intramuscular benzathine penicillin G, with notable improvement of the rash and arthritis symptoms at 2-week follow-up.

Syphilis is a sexually transmitted infection caused by the spirochete T pallidum that progresses through active and latent stages. The incidence of both the primary and secondary stages of syphilis was at a historic low in the year 2000 and has increased annually since then.¹ Syphilis is more common in men, and men who have sex with men (MSM) are disproportionately affected. Although the incidence of syphilis in MSM has increased since 2000, rates have slowed, with slight decreases in this population between 2019 and 2020.¹ Conversely, rates among women have increased substantially in recent years, suggesting a more recent epidemic affecting heterosexual men and women.²

Classically, the primary stage of syphilis manifests as an asymptomatic papule followed by a painless ulcer (chancre) that heals spontaneously. The secondary stage of syphilis results from dissemination of T pallidum and is characterized by a wide range of mucocutaneous manifestations and prodromal symptoms. The most common cutaneous manifestation is a diffuse, nonpruritic, papulosquamous rash with red-brown scaly macules or papules on the trunk and extremities.³ The palms and soles commonly are involved. Mucosal patches, “snail-track” ulcers in the mouth, and condylomata lata are the characteristic mucosal lesions of secondary syphilis. Mucocutaneous findings typically are preceded by systemic signs including fever, malaise, myalgia, and generalized lymphadenopathy. However, syphilis is considered “the great mimicker,” with new reports of unusual presentations of the disease. In addition to papulosquamous morphologies, pustular, targetoid, psoriasiform, and noduloulcerative (also known as lues maligna) forms of syphilis have been reported.^3-5

The histopathologic features of secondary syphilis also are variable. Classically, secondary syphilis demonstrates vacuolar interface dermatitis and acanthosis with slender elongated rete ridges. Other well-known features include endothelial swelling and the presence of plasma cells in most cases.⁶ However, the histopathologic features of secondary syphilis may vary depending on the morphology of the skin eruption and when the biopsy is taken. Our patient lacked the classic histopathologic features of secondary syphilis. However, because syphilis was in the clinical differential diagnosis, a treponemal stain was ordered and confirmed the diagnosis. Immunohistochemical stains using antibodies to treponemal antigens have a reported sensitivity of 71% to 100% and are highly specific.⁷ Although the combination of endothelial swelling, interstitial inflammation, irregular acanthosis, and elongated rete ridges should raise the possibility of syphilis, a treponemal stain may be useful to identify spirochetes if clinical suspicion exists.⁸

Given our patient’s known history of GPA, leukocytoclastic vasculitis was high on the list of differential diagnoses. However, leukocytoclastic vasculitis most classically manifests as petechiae and palpable purpura, and unlike in secondary syphilis, the palms and soles are less commonly involved. Because our patient’s rash was mainly localized to the lower limbs, the differential also included 2 pigmented purpuric dermatoses (PPDs): progressive pigmentary purpura (Schamberg disease) and purpura annularis telangiectodes (Majocchi disease). Progressive pigmentary purpura is the most common manifestation of PPD and appears as cayenne pepper–colored macules that coalesce into golden brown–pigmented patches on the legs.⁹ Purpura annularis telangiectodes is another variant of PPD that manifests as pinpoint telangiectatic macules that progress to annular hyperpigmented patches with central clearing. Although PPDs frequently occur on the lower extremities, reports of plantar involvement are rare.¹⁰ Annular lichen planus manifests as violaceous papules with a clear center; however, it would be atypical for these lesions to be restricted to the feet and ankles. Palmoplantar lichen planus can mimic secondary syphilis clinically, but these cases manifest as hyperkeratotic pruritic papules on the palms and soles in contrast to the faint brown asymptomatic macules noted in our case.¹¹

Our case highlights an unusual presentation of secondary syphilis and demonstrates the challenge of diagnosing this entity on clinical presentation alone. Because this patient lacked the classic clinical and histopathologic features of secondary syphilis, a skin biopsy with positive immunohistochemical staining for treponemal antigens was necessary to make the diagnosis. Given the variability in presentation of secondary syphilis, a biopsy or serologic testing may be necessary to make a proper diagnosis.

The Diagnosis: Mycobacterial Infection

An injury sustained in a wet environment that results in chronic indolent abscesses, nodules, or draining sinus tracts suggests a mycobacterial infection. In our patient, a culture revealed MycobacteriuM fortuitum, which is classified in the rapid grower nontuberculous mycobacteria (NTM) group, along with Mycobacterium chelonae and Mycobacterium abscessus.¹ The patient’s history of skin injury while cutting wet grass and the common presence of M fortuitum in the environment suggested that the organism entered the wound. The patient healed completely following surgical excision and a 2-month course of clarithromycin 1 g daily and rifampin 600 mg daily.

MycobacteriuM fortuitum was first isolated from an amphibian source in 1905 and later identified in a human with cutaneous infection in 1938. It commonly is found in soil and water.2 Skin and soft-tissue infections with M fortuitum usually are acquired from direct entry of the organism through a damaged skin barrier from trauma, medical injection, surgery, or tattoo placement.^2,3

Skin lesions caused by NTM often are nonspecific and can mimic a variety of other dermatologic conditions, making clinical diagnosis challenging. As such, cutaneous manifestations of M fortuitum infection can include recurrent cutaneous abscesses, nodular lesions, chronic discharging sinuses, cellulitis, and surgical site infections.4 Although cutaneous infection with M fortuitum classically manifests with a single subcutaneous nodule at the site of trauma or surgery,⁵ it also can manifest as multiple draining sinus tracts, as seen in our patient. Hence, the diagnosis and treatment of cutaneous NTM infection is challenging, especially when M fortuitum skin manifestations can take up to 4 to 6 weeks to develop after inoculation. Diagnosis often requires a detailed patient history, tissue cultures, and histopathology.⁵

In recent years, rapid detection with polymerase chain reaction (PCR) techniques has been employed more widely. Notably, a molecular system based on multiplex real-time PCR with high-resolution melting was shown to have a sensitivity of up to 54% for distinguishing M fortuitum from other NTM.⁶ More recently, a 2-step real-time PCR method has demonstrated diagnostic sensitivity and specificity for differentiating NTM from Mycobacterium tuberculosis infections and identifying the causative NTM agent.⁷

Compared to immunocompetent individuals, those who are immunocompromised are more susceptible to less pathogenic strains of NTM, which can cause dissemination and lead to tenosynovitis, myositis, osteomyelitis, and septic arthritis.^8-12 Nonetheless, cases of infections with NTM—including M fortuitum—are becoming harder to treat. Several single nucleotide polymorphisms and point mutations have been demonstrated in the ribosomal RNA methylase gene erm(39) related to clarithromycin resistance and in the rrl gene related to linezolid resistance.¹³ Due to increasing inducible resistance to common classes of antibiotics, such as macrolides and linezolid, treatment of M fortuitum requires multidrug regimens.^13,14 Drug susceptibility testing also may be required, as M fortuitum has shown low resistance to tigecycline, tetracycline, cefmetazole, imipenem, and aminoglycosides (eg, amikacin, tobramycin, neomycin, gentamycin). Surgery is an important adjunctive tool in treating M fortuitum infections; patients with a single lesion are more likely to undergo surgical treatment alone or in combination with antibiotic therapy.¹⁵ More recently, antimicrobial photodynamic therapy has been explored as an alternative to eliminate NTM, including M fortuitum.¹⁶

The differential diagnosis for skin lesions manifesting with draining fistulae and sinus tracts includes conditions with infectious (cellulitis and chromomycosis) and inflammatory (pyoderma gangrenosum [PG] and hidradenitis suppurativa [HS]) causes.

Cellulitis is a common infection of the skin and subcutaneous tissue that predominantly is caused by gram-positive organisms such as β-hemolytic streptococci.¹⁷ Clinical manifestations include acute skin erythema, swelling, tenderness, and warmth. The legs are the most common sites of infection, but any area of the skin can be involved.17 Cellulitis comprises 10% of all infectious disease hospitalizations and up to 11% of all dermatologic admissions.^18,19 It frequently is misdiagnosed, perhaps due to the lack of a reliable confirmatory laboratory test or imaging study, in addition to the plethora of diseases that mimic cellulitis, such as stasis dermatitis, lipodermatosclerosis, contact dermatitis, lymphedema, eosinophilic cellulitis, and papular urticaria.^20,21 The consequences of misdiagnosis include but are not limited to unnecessary hospitalizations, inappropriate antibiotic use, and delayed management of the disease; thus, there is an urgent need for a reliable standard test to confirm the diagnosis, especially among nonspecialist physicians. ²⁰ Most patients with uncomplicated cellulitis can be treated with empiric oral antibiotics that target β-hemolytic streptococci (ie, penicillin V potassium, amoxicillin).¹⁷ Methicillin-resistant Staphylococcus aureus coverage generally is unnecessary for nonpurulent cellulitis, but clinicians can consider adding amoxicillin-clavulanate, dicloxacillin, and cephalexin to the regimen. For purulent cellulitis, incision and drainage should be performed. In severe cases that manifest with sepsis, altered mental status, or hemodynamic instability, inpatient management is required.¹⁷

Chromomycosis (also known as chromoblastomycosis) is a chronic, indolent, granulomatous, suppurative mycosis of the skin and subcutaneous tissue²² that is caused by traumatic inoculation of various fungi of the order Chaetothyriales and family Herpotrichiellaceae, which are present in soil, plants, and decomposing wood. Chromomycosis is prevalent in tropical and subtropical regions.^23,24 Clinically, it manifests as oligosymptomatic or asymptomatic lesions around an infection site that can manifest as papules with centrifugal growth evolving into nodular, verrucous, plaque, tumoral, or atrophic forms.²² Diagnosis is made with direct microscopy using potassium hydroxide, which reveals muriform bodies. Fungal culture in Sabouraud agar also can be used to isolate the causative pathogen.²² Unfortunately, chromomycosis is difficult to treat, with low cure rates and high relapse rates. Antifungal agents combined with surgery, cryotherapy, or thermotherapy often are used, with cure rates ranging from 15% to 80%.^22,25

Pyoderma gangrenosum is a reactive noninfectious inflammatory dermatosis associated with inflammatory bowel disease and rheumatoid arthritis. The exact etiology is not clearly understood, but it generally is considered an autoinflammatory disorder.²⁶ The most common form—classical PG—occurs in approximately 85% of cases and manifests as a painful erythematous lesion that progresses to a blistered or necrotic ulcer. It primarily affects the lower legs but can occur in other body sites.²⁷ The diagnosis is based on clinical symptoms after excluding other similar conditions; histopathology of biopsied wound tissues often are required for confirmation. Treatment of PG starts with fast-acting immunosuppressive drugs (corticosteroids and/or cyclosporine) followed by slowacting immunosuppressive drugs (biologics).²⁶

Hidradenitis suppurativa is a chronic recurrent disease of the hair follicle unit that develops after puberty.²⁸ Clinically, HS manifests with painful nodules, abscesses, chronically draining fistulas, and scarring in areas of the body rich in apocrine glands.^29,30 Treatment of HS is challenging due to its diverse clinical manifestations and unclear etiology. Topical therapy, systemic treatments, biologic agents, surgery, and light therapy have shown variable results.^28,31

The Diagnosis: Mycobacterial Infection

An injury sustained in a wet environment that results in chronic indolent abscesses, nodules, or draining sinus tracts suggests a mycobacterial infection. In our patient, a culture revealed MycobacteriuM fortuitum, which is classified in the rapid grower nontuberculous mycobacteria (NTM) group, along with Mycobacterium chelonae and Mycobacterium abscessus.¹ The patient’s history of skin injury while cutting wet grass and the common presence of M fortuitum in the environment suggested that the organism entered the wound. The patient healed completely following surgical excision and a 2-month course of clarithromycin 1 g daily and rifampin 600 mg daily.

MycobacteriuM fortuitum was first isolated from an amphibian source in 1905 and later identified in a human with cutaneous infection in 1938. It commonly is found in soil and water.2 Skin and soft-tissue infections with M fortuitum usually are acquired from direct entry of the organism through a damaged skin barrier from trauma, medical injection, surgery, or tattoo placement.^2,3

Skin lesions caused by NTM often are nonspecific and can mimic a variety of other dermatologic conditions, making clinical diagnosis challenging. As such, cutaneous manifestations of M fortuitum infection can include recurrent cutaneous abscesses, nodular lesions, chronic discharging sinuses, cellulitis, and surgical site infections.4 Although cutaneous infection with M fortuitum classically manifests with a single subcutaneous nodule at the site of trauma or surgery,⁵ it also can manifest as multiple draining sinus tracts, as seen in our patient. Hence, the diagnosis and treatment of cutaneous NTM infection is challenging, especially when M fortuitum skin manifestations can take up to 4 to 6 weeks to develop after inoculation. Diagnosis often requires a detailed patient history, tissue cultures, and histopathology.⁵

In recent years, rapid detection with polymerase chain reaction (PCR) techniques has been employed more widely. Notably, a molecular system based on multiplex real-time PCR with high-resolution melting was shown to have a sensitivity of up to 54% for distinguishing M fortuitum from other NTM.⁶ More recently, a 2-step real-time PCR method has demonstrated diagnostic sensitivity and specificity for differentiating NTM from Mycobacterium tuberculosis infections and identifying the causative NTM agent.⁷

Compared to immunocompetent individuals, those who are immunocompromised are more susceptible to less pathogenic strains of NTM, which can cause dissemination and lead to tenosynovitis, myositis, osteomyelitis, and septic arthritis.^8-12 Nonetheless, cases of infections with NTM—including M fortuitum—are becoming harder to treat. Several single nucleotide polymorphisms and point mutations have been demonstrated in the ribosomal RNA methylase gene erm(39) related to clarithromycin resistance and in the rrl gene related to linezolid resistance.¹³ Due to increasing inducible resistance to common classes of antibiotics, such as macrolides and linezolid, treatment of M fortuitum requires multidrug regimens.^13,14 Drug susceptibility testing also may be required, as M fortuitum has shown low resistance to tigecycline, tetracycline, cefmetazole, imipenem, and aminoglycosides (eg, amikacin, tobramycin, neomycin, gentamycin). Surgery is an important adjunctive tool in treating M fortuitum infections; patients with a single lesion are more likely to undergo surgical treatment alone or in combination with antibiotic therapy.¹⁵ More recently, antimicrobial photodynamic therapy has been explored as an alternative to eliminate NTM, including M fortuitum.¹⁶

The differential diagnosis for skin lesions manifesting with draining fistulae and sinus tracts includes conditions with infectious (cellulitis and chromomycosis) and inflammatory (pyoderma gangrenosum [PG] and hidradenitis suppurativa [HS]) causes.

Cellulitis is a common infection of the skin and subcutaneous tissue that predominantly is caused by gram-positive organisms such as β-hemolytic streptococci.¹⁷ Clinical manifestations include acute skin erythema, swelling, tenderness, and warmth. The legs are the most common sites of infection, but any area of the skin can be involved.17 Cellulitis comprises 10% of all infectious disease hospitalizations and up to 11% of all dermatologic admissions.^18,19 It frequently is misdiagnosed, perhaps due to the lack of a reliable confirmatory laboratory test or imaging study, in addition to the plethora of diseases that mimic cellulitis, such as stasis dermatitis, lipodermatosclerosis, contact dermatitis, lymphedema, eosinophilic cellulitis, and papular urticaria.^20,21 The consequences of misdiagnosis include but are not limited to unnecessary hospitalizations, inappropriate antibiotic use, and delayed management of the disease; thus, there is an urgent need for a reliable standard test to confirm the diagnosis, especially among nonspecialist physicians. ²⁰ Most patients with uncomplicated cellulitis can be treated with empiric oral antibiotics that target β-hemolytic streptococci (ie, penicillin V potassium, amoxicillin).¹⁷ Methicillin-resistant Staphylococcus aureus coverage generally is unnecessary for nonpurulent cellulitis, but clinicians can consider adding amoxicillin-clavulanate, dicloxacillin, and cephalexin to the regimen. For purulent cellulitis, incision and drainage should be performed. In severe cases that manifest with sepsis, altered mental status, or hemodynamic instability, inpatient management is required.¹⁷

Chromomycosis (also known as chromoblastomycosis) is a chronic, indolent, granulomatous, suppurative mycosis of the skin and subcutaneous tissue²² that is caused by traumatic inoculation of various fungi of the order Chaetothyriales and family Herpotrichiellaceae, which are present in soil, plants, and decomposing wood. Chromomycosis is prevalent in tropical and subtropical regions.^23,24 Clinically, it manifests as oligosymptomatic or asymptomatic lesions around an infection site that can manifest as papules with centrifugal growth evolving into nodular, verrucous, plaque, tumoral, or atrophic forms.²² Diagnosis is made with direct microscopy using potassium hydroxide, which reveals muriform bodies. Fungal culture in Sabouraud agar also can be used to isolate the causative pathogen.²² Unfortunately, chromomycosis is difficult to treat, with low cure rates and high relapse rates. Antifungal agents combined with surgery, cryotherapy, or thermotherapy often are used, with cure rates ranging from 15% to 80%.^22,25

Pyoderma gangrenosum is a reactive noninfectious inflammatory dermatosis associated with inflammatory bowel disease and rheumatoid arthritis. The exact etiology is not clearly understood, but it generally is considered an autoinflammatory disorder.²⁶ The most common form—classical PG—occurs in approximately 85% of cases and manifests as a painful erythematous lesion that progresses to a blistered or necrotic ulcer. It primarily affects the lower legs but can occur in other body sites.²⁷ The diagnosis is based on clinical symptoms after excluding other similar conditions; histopathology of biopsied wound tissues often are required for confirmation. Treatment of PG starts with fast-acting immunosuppressive drugs (corticosteroids and/or cyclosporine) followed by slowacting immunosuppressive drugs (biologics).²⁶

Hidradenitis suppurativa is a chronic recurrent disease of the hair follicle unit that develops after puberty.²⁸ Clinically, HS manifests with painful nodules, abscesses, chronically draining fistulas, and scarring in areas of the body rich in apocrine glands.^29,30 Treatment of HS is challenging due to its diverse clinical manifestations and unclear etiology. Topical therapy, systemic treatments, biologic agents, surgery, and light therapy have shown variable results.^28,31

The Diagnosis: Mycobacterial Infection

An injury sustained in a wet environment that results in chronic indolent abscesses, nodules, or draining sinus tracts suggests a mycobacterial infection. In our patient, a culture revealed MycobacteriuM fortuitum, which is classified in the rapid grower nontuberculous mycobacteria (NTM) group, along with Mycobacterium chelonae and Mycobacterium abscessus.¹ The patient’s history of skin injury while cutting wet grass and the common presence of M fortuitum in the environment suggested that the organism entered the wound. The patient healed completely following surgical excision and a 2-month course of clarithromycin 1 g daily and rifampin 600 mg daily.

MycobacteriuM fortuitum was first isolated from an amphibian source in 1905 and later identified in a human with cutaneous infection in 1938. It commonly is found in soil and water.2 Skin and soft-tissue infections with M fortuitum usually are acquired from direct entry of the organism through a damaged skin barrier from trauma, medical injection, surgery, or tattoo placement.^2,3

Skin lesions caused by NTM often are nonspecific and can mimic a variety of other dermatologic conditions, making clinical diagnosis challenging. As such, cutaneous manifestations of M fortuitum infection can include recurrent cutaneous abscesses, nodular lesions, chronic discharging sinuses, cellulitis, and surgical site infections.4 Although cutaneous infection with M fortuitum classically manifests with a single subcutaneous nodule at the site of trauma or surgery,⁵ it also can manifest as multiple draining sinus tracts, as seen in our patient. Hence, the diagnosis and treatment of cutaneous NTM infection is challenging, especially when M fortuitum skin manifestations can take up to 4 to 6 weeks to develop after inoculation. Diagnosis often requires a detailed patient history, tissue cultures, and histopathology.⁵

In recent years, rapid detection with polymerase chain reaction (PCR) techniques has been employed more widely. Notably, a molecular system based on multiplex real-time PCR with high-resolution melting was shown to have a sensitivity of up to 54% for distinguishing M fortuitum from other NTM.⁶ More recently, a 2-step real-time PCR method has demonstrated diagnostic sensitivity and specificity for differentiating NTM from Mycobacterium tuberculosis infections and identifying the causative NTM agent.⁷

Compared to immunocompetent individuals, those who are immunocompromised are more susceptible to less pathogenic strains of NTM, which can cause dissemination and lead to tenosynovitis, myositis, osteomyelitis, and septic arthritis.^8-12 Nonetheless, cases of infections with NTM—including M fortuitum—are becoming harder to treat. Several single nucleotide polymorphisms and point mutations have been demonstrated in the ribosomal RNA methylase gene erm(39) related to clarithromycin resistance and in the rrl gene related to linezolid resistance.¹³ Due to increasing inducible resistance to common classes of antibiotics, such as macrolides and linezolid, treatment of M fortuitum requires multidrug regimens.^13,14 Drug susceptibility testing also may be required, as M fortuitum has shown low resistance to tigecycline, tetracycline, cefmetazole, imipenem, and aminoglycosides (eg, amikacin, tobramycin, neomycin, gentamycin). Surgery is an important adjunctive tool in treating M fortuitum infections; patients with a single lesion are more likely to undergo surgical treatment alone or in combination with antibiotic therapy.¹⁵ More recently, antimicrobial photodynamic therapy has been explored as an alternative to eliminate NTM, including M fortuitum.¹⁶

The differential diagnosis for skin lesions manifesting with draining fistulae and sinus tracts includes conditions with infectious (cellulitis and chromomycosis) and inflammatory (pyoderma gangrenosum [PG] and hidradenitis suppurativa [HS]) causes.

Cellulitis is a common infection of the skin and subcutaneous tissue that predominantly is caused by gram-positive organisms such as β-hemolytic streptococci.¹⁷ Clinical manifestations include acute skin erythema, swelling, tenderness, and warmth. The legs are the most common sites of infection, but any area of the skin can be involved.17 Cellulitis comprises 10% of all infectious disease hospitalizations and up to 11% of all dermatologic admissions.^18,19 It frequently is misdiagnosed, perhaps due to the lack of a reliable confirmatory laboratory test or imaging study, in addition to the plethora of diseases that mimic cellulitis, such as stasis dermatitis, lipodermatosclerosis, contact dermatitis, lymphedema, eosinophilic cellulitis, and papular urticaria.^20,21 The consequences of misdiagnosis include but are not limited to unnecessary hospitalizations, inappropriate antibiotic use, and delayed management of the disease; thus, there is an urgent need for a reliable standard test to confirm the diagnosis, especially among nonspecialist physicians. ²⁰ Most patients with uncomplicated cellulitis can be treated with empiric oral antibiotics that target β-hemolytic streptococci (ie, penicillin V potassium, amoxicillin).¹⁷ Methicillin-resistant Staphylococcus aureus coverage generally is unnecessary for nonpurulent cellulitis, but clinicians can consider adding amoxicillin-clavulanate, dicloxacillin, and cephalexin to the regimen. For purulent cellulitis, incision and drainage should be performed. In severe cases that manifest with sepsis, altered mental status, or hemodynamic instability, inpatient management is required.¹⁷

Chromomycosis (also known as chromoblastomycosis) is a chronic, indolent, granulomatous, suppurative mycosis of the skin and subcutaneous tissue²² that is caused by traumatic inoculation of various fungi of the order Chaetothyriales and family Herpotrichiellaceae, which are present in soil, plants, and decomposing wood. Chromomycosis is prevalent in tropical and subtropical regions.^23,24 Clinically, it manifests as oligosymptomatic or asymptomatic lesions around an infection site that can manifest as papules with centrifugal growth evolving into nodular, verrucous, plaque, tumoral, or atrophic forms.²² Diagnosis is made with direct microscopy using potassium hydroxide, which reveals muriform bodies. Fungal culture in Sabouraud agar also can be used to isolate the causative pathogen.²² Unfortunately, chromomycosis is difficult to treat, with low cure rates and high relapse rates. Antifungal agents combined with surgery, cryotherapy, or thermotherapy often are used, with cure rates ranging from 15% to 80%.^22,25

Pyoderma gangrenosum is a reactive noninfectious inflammatory dermatosis associated with inflammatory bowel disease and rheumatoid arthritis. The exact etiology is not clearly understood, but it generally is considered an autoinflammatory disorder.²⁶ The most common form—classical PG—occurs in approximately 85% of cases and manifests as a painful erythematous lesion that progresses to a blistered or necrotic ulcer. It primarily affects the lower legs but can occur in other body sites.²⁷ The diagnosis is based on clinical symptoms after excluding other similar conditions; histopathology of biopsied wound tissues often are required for confirmation. Treatment of PG starts with fast-acting immunosuppressive drugs (corticosteroids and/or cyclosporine) followed by slowacting immunosuppressive drugs (biologics).²⁶

Hidradenitis suppurativa is a chronic recurrent disease of the hair follicle unit that develops after puberty.²⁸ Clinically, HS manifests with painful nodules, abscesses, chronically draining fistulas, and scarring in areas of the body rich in apocrine glands.^29,30 Treatment of HS is challenging due to its diverse clinical manifestations and unclear etiology. Topical therapy, systemic treatments, biologic agents, surgery, and light therapy have shown variable results.^28,31

The Diagnosis: Pityriasis Lichenoides et Varioliformis Acuta

Sectioned punch biopsies were performed on the patient’s right arm. Histopathology showed acanthosis and parakeratosis in the epidermis, with vacuolar degeneration and dyskeratosis in the basal layer. Dermal changes included extravasated red blood cells in the papillary dermis as well as perivascular lymphocytic infiltrates in both the papillary and reticular dermis (Figure). Direct immunofluorescence of a perilesional biopsy using anti–human IgG, IgM, IgA, C3, and fibrin conjugates showed no findings of immune deposition. Biopsy results were consistent with pityriasis lichenoides et varioliformis acuta (PLEVA), and the patient was treated with a 5-day course of oral azithromycin, triamcinolone ointment 0.1% twice daily, and phototherapy with narrowband UVB ³ times weekly. Rapid improvement was noted at 2-month follow-up.

Pityriasis lichenoides et varioliformis acuta is a form of pityriasis lichenoides, a group of inflammatory dermatoses that are characterized clinically by successive crops of morphologically diverse lesions. Epidemiologic studies have shown a slight male predominance. It primarily affects children and young adults, with peak ages of 8 and 32 years in pediatric and adult populations, respectively.¹

The pathogenesis of PLEVA remains unclear. An abnormal immune response to Toxoplasma, Epstein-Barr virus, HIV, and other pathogens has been suggested based on serologic evidence of concurrent disease activity with the onset of lesions as well as cutaneous improvement in some patients after treatment of the infection.¹ A T-cell lymphoproliferative etiology also has been considered based on histopathologic similarities between PLEVA and lymphomatoid papulosis (LyP) as well as findings of clonality in T-cell receptor gene rearrangement in many patients.^1,2 Some clinicians consider LyP and PLEVA as separate entities on one disease spectrum.

Eruptions of PLEVA tend to favor the trunk and proximal extremities. Lesions may begin as macules measuring 2 to 3 mm in diameter that quickly evolve into papules with fine scale that remains attached centrally. Ulcerations with hemorrhagic crusts also may be noted as the lesions progress in stage. The rash may persist for weeks to years, and overlapping crops of macules and papules at varying stages of development may be seen in the same patient.¹

Histopathologic findings of PLEVA include spongiosis, dyskeratosis, parakeratosis, and focal keratinocyte necrosis within the epidermis, as well as vacuolar degeneration of the basal layer. Lymphocyte and erythrocyte extravasation may extend into the epidermis. Dermal findings may include edema and wedge-shaped perivascular lymphocytic infiltrates extending into the reticular dermis.¹

Important differential diagnoses to consider include LyP, mycosis fungoides (MF), pemphigus foliaceus, and varicella. Lymphomatoid papulosis is a benign CD30+ lymphoproliferative disorder that is characterized by an indolent course of recurrent, often self-resolving papules that occur most frequently on the trunk, arms, and legs of older patients. There are several histologic subtypes of LyP, but the most common (type A) may manifest with wedge-shaped perivascular lymphocytic infiltrates in the dermis, similar to PLEVA. T-cell receptor gene rearrangement studies characteristically reveal clonality in LyP, and clonality has been reported in PLEVA. However, LyP demonstrates a higher cytologic grade and lacks the characteristic parakeratotic scale and superficial dermal microhemorrhage of PLEVA.³

Mycosis fungoides is a malignant lymphoproliferative disorder that is characterized by an indolent clinical course of persistent patches, plaques, or tumors of various sizes that often manifest in non–sun-exposed areas of the skin. Early stages of MF are difficult to detect histologically, but biopsies may show atypical lymphocytes with hyperchromatic, irregularly contoured nuclei arranged along the basal layer of the epidermis. Epidermal aggregates of atypical lymphocytes (also known as Pautrier microabscesses) are considered highly specific for MF. T-cell receptor and immunopathologic studies also are important adjuncts in the diagnosis of MF.⁴

Pemphigus foliaceus is an autoimmune blistering disease caused by antibodies directed against desmoglein 1, which is found in the granular layer of the epidermis. It manifests with a subtle onset of scattered crusted lesions in the seborrheic areas, such as the scalp, face, chest, and upper back. Histopathologic findings of early blisters may include acantholysis and dyskeratosis in the stratum granulosum as well as vacuolization of the granular layer. The blisters may coalesce into superficial bullae containing fibrin and neutrophils. Immunofluorescence studies that demonstrate intraepidermal C3 and IgG deposition are key to the diagnosis of pemphigus.⁵

Varicella (also known as chickenpox) manifests with crops of vesicles on an erythematous base in a centripetal distribution favoring the trunk and proximal extremities. It often is preceded by prodromal fever, malaise, and myalgia. Histopathologic evaluation of varicella is uncommon but may reveal acantholysis, multinucleation, and nuclear margination of keratinocytes. Viral culture or nucleic acid amplification testing of lesions can be used to verify the diagnosis.⁶

Most cases of PLEVA resolve without intervention.7 Treatment is directed at speeding recovery, providing symptomatic relief, and limiting permanent sequelae. Topical steroids often are used to alleviate inflammation and pruritus. Systemic antibiotics such as doxycycline, minocycline, and erythromycin have been used for their anti-inflammatory properties. Phototherapy of various wavelengths, including broadband and narrowband UVB as well as psoralen plus UVA, have led to improvements in affected patients. Refractory disease may warrant consideration of therapy with methotrexate, acitretin, dapsone, or cyclosporine.⁷

There have been rare reports of PLEVA evolving into its potentially lethal variant, febrile ulceronecrotic Mucha-Habermann disease, which is differentiated by the presence of systemic manifestations, including high fever, sore throat, diarrhea, central nervous system symptoms, abdominal pain, interstitial pneumonitis, splenomegaly, arthritis, sepsis, megaloblastic anemia, or conjunctival ulcers. The orogenital mucosa may be affected. Cutaneous lesions may rapidly progress to large, generalized, coalescent ulcers with necrotic crusts and vasculitic features on biopsy.8 Malignant transformation of PLEVA into LyP or MF rarely may occur and warrants continued follow-up of unresolved lesions.⁹

The Diagnosis: Pityriasis Lichenoides et Varioliformis Acuta

Sectioned punch biopsies were performed on the patient’s right arm. Histopathology showed acanthosis and parakeratosis in the epidermis, with vacuolar degeneration and dyskeratosis in the basal layer. Dermal changes included extravasated red blood cells in the papillary dermis as well as perivascular lymphocytic infiltrates in both the papillary and reticular dermis (Figure). Direct immunofluorescence of a perilesional biopsy using anti–human IgG, IgM, IgA, C3, and fibrin conjugates showed no findings of immune deposition. Biopsy results were consistent with pityriasis lichenoides et varioliformis acuta (PLEVA), and the patient was treated with a 5-day course of oral azithromycin, triamcinolone ointment 0.1% twice daily, and phototherapy with narrowband UVB ³ times weekly. Rapid improvement was noted at 2-month follow-up.

Pityriasis lichenoides et varioliformis acuta is a form of pityriasis lichenoides, a group of inflammatory dermatoses that are characterized clinically by successive crops of morphologically diverse lesions. Epidemiologic studies have shown a slight male predominance. It primarily affects children and young adults, with peak ages of 8 and 32 years in pediatric and adult populations, respectively.¹

The pathogenesis of PLEVA remains unclear. An abnormal immune response to Toxoplasma, Epstein-Barr virus, HIV, and other pathogens has been suggested based on serologic evidence of concurrent disease activity with the onset of lesions as well as cutaneous improvement in some patients after treatment of the infection.¹ A T-cell lymphoproliferative etiology also has been considered based on histopathologic similarities between PLEVA and lymphomatoid papulosis (LyP) as well as findings of clonality in T-cell receptor gene rearrangement in many patients.^1,2 Some clinicians consider LyP and PLEVA as separate entities on one disease spectrum.

Eruptions of PLEVA tend to favor the trunk and proximal extremities. Lesions may begin as macules measuring 2 to 3 mm in diameter that quickly evolve into papules with fine scale that remains attached centrally. Ulcerations with hemorrhagic crusts also may be noted as the lesions progress in stage. The rash may persist for weeks to years, and overlapping crops of macules and papules at varying stages of development may be seen in the same patient.¹

Histopathologic findings of PLEVA include spongiosis, dyskeratosis, parakeratosis, and focal keratinocyte necrosis within the epidermis, as well as vacuolar degeneration of the basal layer. Lymphocyte and erythrocyte extravasation may extend into the epidermis. Dermal findings may include edema and wedge-shaped perivascular lymphocytic infiltrates extending into the reticular dermis.¹

Important differential diagnoses to consider include LyP, mycosis fungoides (MF), pemphigus foliaceus, and varicella. Lymphomatoid papulosis is a benign CD30+ lymphoproliferative disorder that is characterized by an indolent course of recurrent, often self-resolving papules that occur most frequently on the trunk, arms, and legs of older patients. There are several histologic subtypes of LyP, but the most common (type A) may manifest with wedge-shaped perivascular lymphocytic infiltrates in the dermis, similar to PLEVA. T-cell receptor gene rearrangement studies characteristically reveal clonality in LyP, and clonality has been reported in PLEVA. However, LyP demonstrates a higher cytologic grade and lacks the characteristic parakeratotic scale and superficial dermal microhemorrhage of PLEVA.³

Mycosis fungoides is a malignant lymphoproliferative disorder that is characterized by an indolent clinical course of persistent patches, plaques, or tumors of various sizes that often manifest in non–sun-exposed areas of the skin. Early stages of MF are difficult to detect histologically, but biopsies may show atypical lymphocytes with hyperchromatic, irregularly contoured nuclei arranged along the basal layer of the epidermis. Epidermal aggregates of atypical lymphocytes (also known as Pautrier microabscesses) are considered highly specific for MF. T-cell receptor and immunopathologic studies also are important adjuncts in the diagnosis of MF.⁴

Pemphigus foliaceus is an autoimmune blistering disease caused by antibodies directed against desmoglein 1, which is found in the granular layer of the epidermis. It manifests with a subtle onset of scattered crusted lesions in the seborrheic areas, such as the scalp, face, chest, and upper back. Histopathologic findings of early blisters may include acantholysis and dyskeratosis in the stratum granulosum as well as vacuolization of the granular layer. The blisters may coalesce into superficial bullae containing fibrin and neutrophils. Immunofluorescence studies that demonstrate intraepidermal C3 and IgG deposition are key to the diagnosis of pemphigus.⁵

Varicella (also known as chickenpox) manifests with crops of vesicles on an erythematous base in a centripetal distribution favoring the trunk and proximal extremities. It often is preceded by prodromal fever, malaise, and myalgia. Histopathologic evaluation of varicella is uncommon but may reveal acantholysis, multinucleation, and nuclear margination of keratinocytes. Viral culture or nucleic acid amplification testing of lesions can be used to verify the diagnosis.⁶

Most cases of PLEVA resolve without intervention.7 Treatment is directed at speeding recovery, providing symptomatic relief, and limiting permanent sequelae. Topical steroids often are used to alleviate inflammation and pruritus. Systemic antibiotics such as doxycycline, minocycline, and erythromycin have been used for their anti-inflammatory properties. Phototherapy of various wavelengths, including broadband and narrowband UVB as well as psoralen plus UVA, have led to improvements in affected patients. Refractory disease may warrant consideration of therapy with methotrexate, acitretin, dapsone, or cyclosporine.⁷

There have been rare reports of PLEVA evolving into its potentially lethal variant, febrile ulceronecrotic Mucha-Habermann disease, which is differentiated by the presence of systemic manifestations, including high fever, sore throat, diarrhea, central nervous system symptoms, abdominal pain, interstitial pneumonitis, splenomegaly, arthritis, sepsis, megaloblastic anemia, or conjunctival ulcers. The orogenital mucosa may be affected. Cutaneous lesions may rapidly progress to large, generalized, coalescent ulcers with necrotic crusts and vasculitic features on biopsy.8 Malignant transformation of PLEVA into LyP or MF rarely may occur and warrants continued follow-up of unresolved lesions.⁹

The Diagnosis: Pityriasis Lichenoides et Varioliformis Acuta

Sectioned punch biopsies were performed on the patient’s right arm. Histopathology showed acanthosis and parakeratosis in the epidermis, with vacuolar degeneration and dyskeratosis in the basal layer. Dermal changes included extravasated red blood cells in the papillary dermis as well as perivascular lymphocytic infiltrates in both the papillary and reticular dermis (Figure). Direct immunofluorescence of a perilesional biopsy using anti–human IgG, IgM, IgA, C3, and fibrin conjugates showed no findings of immune deposition. Biopsy results were consistent with pityriasis lichenoides et varioliformis acuta (PLEVA), and the patient was treated with a 5-day course of oral azithromycin, triamcinolone ointment 0.1% twice daily, and phototherapy with narrowband UVB ³ times weekly. Rapid improvement was noted at 2-month follow-up.

Pityriasis lichenoides et varioliformis acuta is a form of pityriasis lichenoides, a group of inflammatory dermatoses that are characterized clinically by successive crops of morphologically diverse lesions. Epidemiologic studies have shown a slight male predominance. It primarily affects children and young adults, with peak ages of 8 and 32 years in pediatric and adult populations, respectively.¹

The pathogenesis of PLEVA remains unclear. An abnormal immune response to Toxoplasma, Epstein-Barr virus, HIV, and other pathogens has been suggested based on serologic evidence of concurrent disease activity with the onset of lesions as well as cutaneous improvement in some patients after treatment of the infection.¹ A T-cell lymphoproliferative etiology also has been considered based on histopathologic similarities between PLEVA and lymphomatoid papulosis (LyP) as well as findings of clonality in T-cell receptor gene rearrangement in many patients.^1,2 Some clinicians consider LyP and PLEVA as separate entities on one disease spectrum.

Eruptions of PLEVA tend to favor the trunk and proximal extremities. Lesions may begin as macules measuring 2 to 3 mm in diameter that quickly evolve into papules with fine scale that remains attached centrally. Ulcerations with hemorrhagic crusts also may be noted as the lesions progress in stage. The rash may persist for weeks to years, and overlapping crops of macules and papules at varying stages of development may be seen in the same patient.¹

Histopathologic findings of PLEVA include spongiosis, dyskeratosis, parakeratosis, and focal keratinocyte necrosis within the epidermis, as well as vacuolar degeneration of the basal layer. Lymphocyte and erythrocyte extravasation may extend into the epidermis. Dermal findings may include edema and wedge-shaped perivascular lymphocytic infiltrates extending into the reticular dermis.¹

Important differential diagnoses to consider include LyP, mycosis fungoides (MF), pemphigus foliaceus, and varicella. Lymphomatoid papulosis is a benign CD30+ lymphoproliferative disorder that is characterized by an indolent course of recurrent, often self-resolving papules that occur most frequently on the trunk, arms, and legs of older patients. There are several histologic subtypes of LyP, but the most common (type A) may manifest with wedge-shaped perivascular lymphocytic infiltrates in the dermis, similar to PLEVA. T-cell receptor gene rearrangement studies characteristically reveal clonality in LyP, and clonality has been reported in PLEVA. However, LyP demonstrates a higher cytologic grade and lacks the characteristic parakeratotic scale and superficial dermal microhemorrhage of PLEVA.³

Mycosis fungoides is a malignant lymphoproliferative disorder that is characterized by an indolent clinical course of persistent patches, plaques, or tumors of various sizes that often manifest in non–sun-exposed areas of the skin. Early stages of MF are difficult to detect histologically, but biopsies may show atypical lymphocytes with hyperchromatic, irregularly contoured nuclei arranged along the basal layer of the epidermis. Epidermal aggregates of atypical lymphocytes (also known as Pautrier microabscesses) are considered highly specific for MF. T-cell receptor and immunopathologic studies also are important adjuncts in the diagnosis of MF.⁴

Pemphigus foliaceus is an autoimmune blistering disease caused by antibodies directed against desmoglein 1, which is found in the granular layer of the epidermis. It manifests with a subtle onset of scattered crusted lesions in the seborrheic areas, such as the scalp, face, chest, and upper back. Histopathologic findings of early blisters may include acantholysis and dyskeratosis in the stratum granulosum as well as vacuolization of the granular layer. The blisters may coalesce into superficial bullae containing fibrin and neutrophils. Immunofluorescence studies that demonstrate intraepidermal C3 and IgG deposition are key to the diagnosis of pemphigus.⁵

Varicella (also known as chickenpox) manifests with crops of vesicles on an erythematous base in a centripetal distribution favoring the trunk and proximal extremities. It often is preceded by prodromal fever, malaise, and myalgia. Histopathologic evaluation of varicella is uncommon but may reveal acantholysis, multinucleation, and nuclear margination of keratinocytes. Viral culture or nucleic acid amplification testing of lesions can be used to verify the diagnosis.⁶

Most cases of PLEVA resolve without intervention.7 Treatment is directed at speeding recovery, providing symptomatic relief, and limiting permanent sequelae. Topical steroids often are used to alleviate inflammation and pruritus. Systemic antibiotics such as doxycycline, minocycline, and erythromycin have been used for their anti-inflammatory properties. Phototherapy of various wavelengths, including broadband and narrowband UVB as well as psoralen plus UVA, have led to improvements in affected patients. Refractory disease may warrant consideration of therapy with methotrexate, acitretin, dapsone, or cyclosporine.⁷

There have been rare reports of PLEVA evolving into its potentially lethal variant, febrile ulceronecrotic Mucha-Habermann disease, which is differentiated by the presence of systemic manifestations, including high fever, sore throat, diarrhea, central nervous system symptoms, abdominal pain, interstitial pneumonitis, splenomegaly, arthritis, sepsis, megaloblastic anemia, or conjunctival ulcers. The orogenital mucosa may be affected. Cutaneous lesions may rapidly progress to large, generalized, coalescent ulcers with necrotic crusts and vasculitic features on biopsy.8 Malignant transformation of PLEVA into LyP or MF rarely may occur and warrants continued follow-up of unresolved lesions.⁹