An Adult-Onset Case of Porokeratotic Eccrine Ostial and Dermal Duct Nevus (PEODDN) in a Previously Healthy 28-Year-Old Indian Male: A Case Report.

A 28-year-old Indian male with no previous medical or dermatological history presented with mildly pruritic linear skin lesions over the right anterior chest and arm. The lesions had been gradually progressing over the course of six years. Examination revealed multiple confluent, reddish-brown papules following Blaschko's lines, along with punctate hyperkeratotic papules over the right hand, with sparing of the mucosa, scalp, and nails. Histopathological analysis demonstrated a cup-shaped epidermal invagination filled with a parakeratotic column, absence of the granular layer, and dyskeratotic keratinocytes, with an eccrine duct located at the base of the lesion - indicating an acrosyringial origin. These findings confirmed the diagnosis of porokeratotic eccrine ostial and dermal duct nevus (PEODDN). PEODDN is a rare hamartomatous disorder with eccrine differentiation. While it usually presents at birth or during childhood, adult-onset cases have been documented - particularly along Blaschko's lines. The condition may present with porokeratotic plaques or comedo-like plugs on acral sites, and our case uniquely exhibited both features. Although its pathogenesis remains unclear, several theories suggest abnormal keratinization, structural defects in eccrine ducts, and possible genetic mutations. PEODDN may occasionally be associated with systemic or neoplastic conditions. Treatment options remain variable, and while no standard therapy offers complete resolution, our findings support the potential role of oral retinoids in improving lesion appearance and symptoms in adult-onset cases. Further evaluation of systemic retinoid therapy in PEODDN is warranted.