Porokeratosis ptychotropica with scalp involvement: A case report

Abstract

Porokeratosis, a spectrum of disorders characterized by abnormal keratinization, includes the rare variant porokeratosis ptychotropica, which typically manifests with hyperkeratotic plaques on the buttocks and genital area. Its clinical mimicry to various skin diseases and under-recognition frequently result in misdiagnosis. This challenge is compounded by the resistance of porokeratosis ptychotropica to treatment. Herein, we report a 62-year-old Thai male with persistent pruritic hypertrophic plaques that affected his genitogluteal area, extremities, and scalp over 5 years, which was unresponsive to diverse topical agents. Histopathological findings revealed an acanthotic epidermis with a cornoid lamella, consistent with porokeratosis ptychotropica. Acitretin was administered orally at a dosage of 25 mg every other day to 25 mg daily for 7 months, resulting in significant improvement. This report introduces the first documented case of porokeratosis ptychotropica with scalp involvement, expanding our understanding of disease manifestations. Although its treatment poses challenges because of resistance to many conventional treatments, this patient exhibited remarkable improvement after the oral intake of acitretin.