Abstract
Porokeratosis represents a group of disorders of epidermal keratinization that are characterized by one or more annular plaques surrounded by a histologically distinctive hyperkeratotic ridge-like border called the cornoid lamella. Many studies showed that organ transplantation and immunosuppression were associated in a significant number of cases. Furthermore, an association with squamous cell carcinoma and basal cell carcinoma has been noted in all variants of porokeratosis. The rarity of this disorder and its atypical clinical presentation - a single lesion on the thumb of an HIV-positive male patient - motivated this report.