Multiple keratotic papules on palm.

Porokeratotic eccrine ostial and dermal duct nevus (PEODDN) is a rare nonhereditary malformation of the eccrine duct. A relationship with linear porokeratosis is not yet established; some consider it as a rare variant of porokeratosis involving the acrosyringium, whereas others consider it a separate entity based on distinctive clinical features and histologic accentuation within ostial structures. A 7-year-old girl presented with multiple asymptomatic keratotic papules over her right palm, present since the age of 6 months. These papules were arranged in a linear distribution over the palm and middle finger of the right hand. Most of the papules were discrete. However, lesions on the middle finger coalesced to form a plaque. Histology revealed a keratin filled deep invagination of the epidermis, notable for a column of parakeratosis ("cornoid lamella"). The dermis was notable for dilated eccrine ducts and absent inflammation. Considering the clinical and histological evidence, a diagnosis of PEODDN was made. Its clinical resemblance to linear lichen planus and linear porokeratosis is discussed. Also, we provide a brief review of this rare condition.