Porokeratotic eccrine ostial and dermal duct nevus. Report of a case of adult onset.

We describe the case of a 38-year-old woman with adult-onset porokeratotic eccrine ostial and dermal duct nevus. The patient had a 9-year history of multiple keratotic papules and comedo-like pits on the medial border of the left foot. Light- and electron microscopic studies showed multiple cornoid lamella-like parakeratotic columns, which invariably were associated with hyperplastic eccrine ostia and distal sweat ducts. It is concluded that this entity, the first reported case of adult-onset porokeratotic eccrine ostial and dermal duct nevus, is a variant of the congenital form described previously by Abell and Read and by Aloi and Pippione.