Genitogluteal porokeratosis involving the scrotum: an unusual presentation of an uncommon disease.

Porokeratosis represents a heterogeneous group of keratinization disorders typified by the presence of annular plaques with distinct, raised borders that include cornoid lamellae. Histopathologically, a cornoid lamella is a column of parakeratotic scale overlying an epidermal invagination that displays nearby dyskeratotic keratinocytes and loss of the granular layer. Porokeratosis ptychotropica constitutes a rare variant that classically presents as a plaque in the gluteal cleft that mimics a dermatitis and microscopically contains numerous cornoid lamellae. We report a 28 year-old man with a two-month history of scrotal burning and itching associated with the development of multiple thin red plaques with distinct elevated borders and a pebbled appearance. Histopathological examination revealed psoriasiform acanthosis and multiple cornoid lamellae, which is consistent with a diagnosis of porokeratosis ptychotropica. Our patient's presentation may represent a distinct variant with clinical features of verrucous porokeratosis and histopathological features of porokeratosis ptychotropica which may suggest that the finding of multiple cornoid lamellae is not unique to porokeratosis ptychotropica.