Adult-Onset Porokeratotic Eccrine Ostial and Dermal Duct Nevus: Dermatoscopic Findings and Treatment with Tazarotene

The document described a case of adult-onset porokeratotic eccrine ostial and dermal duct nevus (PEODDN), a rare skin condition with only 70 reported cases, and detailed its dermatoscopic findings and treatment. The patient, the 8th adult-onset case, was treated with daily applications of tazarotene 0.1% gel, which improved the lesions by reducing erythema and surface hyperkeratosis after one month. Microscopic examination revealed epidermal hyperplasia, parakeratotic plugs within dilated eccrine sweat-gland ostia, and a lymphocytic infiltrate around the eccrine glands, confirming the diagnosis. The condition, which can be mistaken for other dermatoses with linear distribution, is characterized by unilateral, verrucous or keratotic lesions, often on the extremities. The exact cause of PEODDN remains unclear, but it may involve mutant keratinocytes in eccrine glands.