Allogeneic bone marrow transplantation possibly induces a localized type of porokeratosis

A 15-year-old girl underwent allogenic bone marrow transplantation for neuroblastoma. A few years later, she noticed a round lesion on her left buttock. Since the lesion had been asymptomatic and never grown, more than 20 years had passed before she saw a local doctor to consult about it. Although the lesion was suspected to be tinea corporis, no fungi were found on microscopic examination. Subsequently, administered topical corticosteroids were not effective. She was referred to our hospital for further evaluation, and a skin biopsy confirmed the diagnosis of porokeratosis. There was a possibility that chemotherapy, total body radiation, or immunosuppressive therapy associated with allogeneic bone marrow transplantation was involved in the development of porokeratosis. Numerous cases of acquired porokeratosis in immunocompromised status have been observed; as for those after allogenic bone marrow transplantation, 12 cases have been reported in the English literature, 4 of which had only one or a few lesions on a limited area of body surface. Our case was relatively uncommon in that the lesion was solitary and comparatively large. In a localized type of porokeratosis, it was suggested that a malignant skin tumor developed earlier than in other types. Careful follow-up for malignant transformation is especially required.