Make the Diagnosis

Make the Diagnosis - June 2017

A 15-month-old adopted white boy was evaluated for an annular plaque on the right thumb. The lesion began as a small papule at 1 month of age and grew over the course of the following year. The patient’s past medical history was significant for atopic dermatitis and mild developmental delay. His mother reported that he sucked and chewed the affected thumb. There was no history of associated pain or pruritus. The mother reported that the lesion on the thumb flared when his atopic dermatitis worsened. On exam, he was noted to have a 2-cm well-demarcated annular hyperkeratotic plaque.

What is your diagnosis?

linear psoriasis

inflammatory linear verrucous epidermal nevus

porokeratosis of Mibelli

Porokeratotic eccrine ostial and dermal duct nevus (PEODDN)

Diagnosis: Porokeratotic eccrine ostial and dermal duct nevus (PEODDN)

Porokeratotic eccrine ostial and dermal duct nevus (PEODDN) is a rare, benign adnexal hamartoma first reported by Marsden et al. in 1979 as “comedo nevus of the palm” ( Br J Dermatol. 1979 Dec;101[6]:717-22 ).

To date, 77 cases of PEODDN have been reported in the literature, with 53% having congenital onset. The average age of onset for the acquired lesions was 6 years. PEODDN affects males and females equally. Acral location is the most common (94%), but lesions have been reported less commonly on the trunk and face. A review of the literature found that most cases of PEODDN were independent, not associated with other conditions. Rarely, Bowen’s disease and squamous cell carcinoma have been reported to arise within PEODDN. Interestingly, two cases have been associated with keratitis-ichthyosis-deafness syndrome (KID).

A somatic mutation in the GJB2 gene, which encodes the gap junction protein connexin 26, has recently been implicated in the pathogenesis of PEODDN. Connexins act as hemichannels between adjacent cells and play a key role in intracellular signaling and extracellular calcium uptake within cells. The GJB2 mutation has been shown to increase hemichannel activity, as well as intracellular calcium concentrations, which aid in cell proliferation, differentiation, and cell adhesion.

Common differential diagnoses for PEODDN include porokeratosis of Mibelli, linear psoriasis, and linear epidermal nevus. Linear porokeratosis and porokeratosis of Mibelli are characterized by sharply demarcated hyperkeratotic annular lesions with distinct keratotic edges but do not have eccrine gland involvement on histopathology. Linear psoriasis, a rare form of psoriasis, is characterized by late onset linear psoriatic lesions along Blaschko lines. Linear epidermal nevus is a disease characterized by pruritic, erythematous scaly lesions following Blaschko lines that occurs in the first months of life and is slowly progressive. Histopathological features of PEODDN are diagnostic and distinguish it from these other clinical entities. A prominent parakeratotic column within an epidermal invagination that displays loss of the granular layer is found overlaying an eccrine duct with a dilated acrosyringium. Vacuolated and dyskeratotic keratinocytes are also typically present within the epidermal invagination.

The treatment for PEODDN remains elusive. Topical keratolytics, topical retinoids, topical steroids, topical calcipotriol, cryosurgery, phototherapy, and anthralin have been used to treat PEODDN unsuccessfully. Thus far, the most efficacious treatments include CO 2 laser and surgical excision for small lesions. Given the young age of this patient, emollient therapy was chosen as treatment until the patient reaches an age at which the lesion is cosmetically more disturbing and other therapies may be safely attempted.

In conclusion, this patient represents a classic case of the rare entity, PEODDN, and draws attention to recent discoveries that a genetic mutation in GJB2 is causative. Because PEODDN shares its pathogenic mutation with KID syndrome, clinicians should be aware that, if the same mutation also affects germline cells, offspring have the potential to express manifestations of KID syndrome.

This case and photo are courtesy of Molly B. Hirt, a medical student at Indiana University, Indianapolis; Carrie L. Davis, MD, of the Dermatology Center of Southern Indiana and Indiana University, Bloomington; and Anita N. Haggstrom, MD, of the departments of dermatology and pediatrics, Indiana University, Indianapolis.


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