A Case Report of Porokeratosis Ptychotropica in a Chinese Man.

Porokeratosis ptychotropica is a rare form of porokeratosis characterized by dyskeratotic skin lesions around genital area or gluteal cleft. Herein, a case of porokeratosis ptychotropica was reported. The patient was a 35-year-old man, who complained of pruritic papules and plaques in the perianal and buttock region for thirteen years. On examination, well-demarcated brown plaques with a verrucous white surface and multiple satellite papules were located along the gluteal folds and buttocks sparing the anus. Histopathological examination was consistent with porokeratosis. Combined with clinical manifestations and histopathologic changes, the patient was diagnosed as porokeratosis ptychotropica. He was treated with oral acitretin 30mg/d and CO2 laser treatment, but the lesions showed no evident improvement after three months. Although it is not a new case, this condition is an extremely rare one that must be reviewed and emphasized. The dermatologist should keep porokeratosis ptychotropica in mind as one differential diagnosis for pruritic papules in the anogenital region.