Rapid development of disseminated superficial porokeratosis after transplant induction therapy

Disseminated superficial actinic porokeratosis (DSAP) is a cutaneous disorder, usually inherited in an autosomal dominant fashion, characterized by numerous annular papules with subtle raised hyperkeratotic borders and slightly atrophic centers. While the precise pathophysiologic mechanisms underlying the development of DSAP are unknown, one hypothesis is multifocal expansion of atypical clones of keratinocytes, perhaps unmasked by actinic damage, as implied by its name. Although primarily of cosmetic concern, there is an increased risk of squamous cell carcinoma of the skin developing within DSAP lesions, which often show histologic keratinocytic atypia centrally. Immunosuppression, which is a significant risk factor for secondary malignancies including cutaneous squamous cell carcinoma, is also a well-documented precipitant of porokeratosis. We report a 62-year-old man who developed DSAP in a widely and rapidly progressive manner within days of receiving total body radiation and high-dose induction chemotherapy as planned preparative therapy for an autologous peripheral blood stem cell transplant for relapsed high grade lymphoma. Our patient's eruption of DSAP highlights a little recognized cutaneous manifestation of aggressive bone marrow transplant induction therapy.