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.

Porokeratotic eccrine ostial and dermal duct nevus (PEODDN) is a rare dermatological disorder with fewer than 100 reported cases. It is characterized by abnormal keratinization over the dilated acrosyringium, and is hypothesized to involve somatic mosaicism of the GJB2 gene. Typically presenting in early childhood with linearly distributed hyperkeratotic papules along the Blaschko line, PEODDN predominantly affects palms and soles. We report an atypical case of PEODDN in a 64-year-old woman who presented with an asymptomatic solitary nodule on her left foot that had been present for three months. Histopathological examination confirmed the diagnosis and revealed a characteristic cornoid lamella overlying the dilated acrosyringium. The lesion was successfully treated with a CO2 laser, with complete resolution and no recurrence at one-month follow-up. This case highlights the importance of considering PEODDN in the differential diagnosis of solitary lesion in atypical locations, even in older adults, and contributes to the limited literature on the late-onset solitary presentation of this rare condition. Our comprehensive review of the literature provides insights into the pathogenesis, clinical variations, associated conditions, and treatment options of PEODDN, with the aim of guiding clinicians in managing this uncommon entity.