Histopathologic examination of a representative lesion from the left trunk area revealed an atrophic epidermis in the central area, while the hyperkeratotic border was characterized by a column of tightly packed parakeratotic cells, signifying a cornoid lamella. A discrete lymphocytic infiltrate was present in the papillary dermis. A biopsy specimen from a papule on the left lower leg area showed an identical picture (not shown).
Porokeratoses can present as distinct clinical variants, including classic porokeratosis of Mibelli, DSAP, LP, porokeratosis punctata palmaris et plantaris, and porokeratosis plantaris palmaris et disseminata.1 In all types, the lesions are characterized by a hyperkeratotic rim that histologically corresponds to the cornoid lamella. Porokeratoses are inherited as an autosomal dominant trait. The loci responsible for DSAP have been mapped to chromosomes 12q, 15q, and 18q.2- 4 Recently, several mutations have been identified in the SSH1 gene on chromosome 12, which encodes a phosphatase that plays a pivotal role in actin dynamics.5
Keratotic Plaques on the Left Trunk Area and All Extremities—Diagnosis. Arch Dermatol. 2006;142(8):1059-1064. doi:10.1001/archderm.142.8.1059-g