Keratosis follicularis.

Keratosis follicularis is a genetic disorder that is inherited in an autosomal dominant pattern. Physical examination classically shows keratotic papules that are distributed mostly on the so-called "seborrheic" areas of the body. Nail involvement is not uncommon and is characterized by V-shaped nicking at the distal aspect of the nail bed, longitudinal red and white alternating bands, and subungual hyperkeratosis. Mucosal membrane involvement may occur as white papules on the buccal mucosae, palate, and gingiva with a cobblestone appearance. The mutation has been traced to chromosome 12, where a spectrum of mutations within the ATP2A2 gene encode the calcium ATPase of the sarco/endoplasmic reticulum (SERCA2).