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Linear Violaceous Papules in a Child

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A 5-year-old Black girl presented to the dermatology clinic with a stable pruritic eruption on the right leg of 1 month’s duration. Over-the-counter hydrocortisone cream was applied for 3 days with no response. Physical examination revealed grouped, flat-topped, violaceous papules coalescing into plaques with overlying lacy white striae along the right lower leg, wrapping around to the right dorsal foot in a blaschkoid distribution. The patient was otherwise healthy and up-to-date on immunizations and had an unremarkable birth history.

What's your diagnosis?

incontinentia pigmenti

inflammatory linear verrucous epidermal nevus

lichen striatus

linear lichen planus

linear psoriasis

The Diagnosis: Linear Lichen Planus

The patient was clinically diagnosed with linear lichen planus and was started on betamethasone dipropionate ointment 0.05% applied once daily with improvement in both the pruritus and appearance at 4-month follow-up. A biopsy was deferred based on the parents’ wishes.

Lichen planus is an inflammatory disorder involving the skin and oral mucosa. Cutaneous lichen planus classically presents as flat-topped, violaceous, pruritic, polygonal papules with overlying fine white or grey lines known as Wickham striae.1 Postinflammatory hyperpigmentation is common, especially in patients with darker skin tones. Expected histologic findings include orthokeratosis, apoptotic keratinocytes, and bandlike lymphocytic infiltration at the dermoepidermal junction.1

An estimated 5% of cases of cutaneous lichen planus occur in children.2 A study of 316 children with lichen planus demonstrated that the classic morphology remained the most common presentation, while the linear variant was present in only 6.9% of pediatric cases.3 Linear lichen planus appears to be more common among children than adults. A study of 36 pediatric cases showed a greater representation of lichen planus in Black children (67% affected vs 21% cohort).2

Cutaneous lichen planus often clears spontaneously in approximately 1 year.4 Treatment in children primarily is focused on shortening the time to resolution and relieving pruritus, with topical corticosteroids as firstline therapy.3,4 Oral corticosteroids have a faster clinical response; greater efficacy; and more effectively prevent residual hyperpigmentation, which is especially relevant in individuals with darker skin.3 Nonetheless, oral corticosteroids are considered a second-line treatment due to their unfavorable side-effect profile. Additional treatment options include oral aromatic retinoids (acitretin) and phototherapy.3

Incontinentia pigmenti is characterized by a defect in the inhibitor of nuclear factor–κB kinase regulatory subunit gamma, IKBKG, gene on the X chromosome. Incontinentia pigmenti usually is lethal in males; in females, it leads to ectodermal dysplasia associated with skin findings in a blaschkoid distribution occurring in 4 stages.5 The verrucous stage is preceded by the vesicular stage and expected to occur within the first few months of life, making it unlikely in our 5-year-old patient. Inflammatory linear verrucous epidermal nevus usually occurs in children younger than 5 years and is characterized by psoriasiform papules coalescing into a plaque with substantial scale instead of Wickham striae, as seen in our patient.6 Lichen striatus consists of smaller, pink to flesh-colored papules that rarely are pruritic.7 It is more common among atopic individuals and is associated with postinflammatory hypopigmentation.8 Linear psoriasis presents similarly to inflammatory linear verrucous epidermal nevus, with greater erythema and scale compared to the fine lacy Wickham striae that were seen in our patient.8

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Update on the Pediatric Dermatology Workforce Shortage

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