Atypical porokeratosis developing following bone marrow transplantation in a patient with myelodysplastic syndrome.

Porokeratosis is an abnormal disease of keratinization of epidermis. It is clinically characterized by margins covered with keratin layer and it typically has an atrophied macule with a protruded, circular form. Histopathologically, it shows the findings of cornoid lamella. Risk factors for its development include organ transplantation, long-term use of corticosteroids, immunocompromised status, including AIDS, and exposure to ultraviolet light. We herein report a case of atypical porokeratosis in a 38-year-old man who developed porokeratosis involving multiple sites following bone marrow transplantation for myelodysplastic syndrome.