Disseminated superficial actinic porokeratosis co-existing with linear and verrucous porokeratosis in an elderly woman: Update on the genetics and clinical expression of porokeratosis

Disseminated superficial actinic porokeratosis (DSAP) is the most common form of porokeratosis, occurring mainly in women on the extremities as atrophic patches rimmed by a ridge of keratin (the cornoid lamella that is diagnostic of porokeratosis histologically and is thought to be a clonal keratinocyte proliferation). DSAP can sometimes coexist with other forms of porokeratosis (Mibelli, linear porokeratosis, porokeratosis palmaris et plantaris disseminata, and punctate porokeratosis). Rare variants of linear porokeratosis are the hyperkeratotic and verrucous forms which usually occur on the buttocks or perianal area. We present clinical and histopathologic findings from biopsy specimens of a 73-year-old woman with DSAP on the distal extremities, linear/segmental porokeratosis on thighs, and verrucous porokeratosis on buttocks and mons pubis. The verrucous lesions had been present for 30+ years, the DSAP and linear lesions for 10+ years. Biopsy specimens from distal extremity showed classic features of DSAP with infrequent cornoid lamellae separated by atrophic epidermis. Biopsy specimens from the mons pubis and thigh showed epidermal hyperplasia with multiple, almost contiguous, broad cornoid lamellae. Coexisting variants of porokeratosis are rare and our conclusions are drawn from a few cases in the literature. The rare variants of porokeratosis are of interest because the clinical morphology correlates with the histopathology.