Iatrogenic Kaposi sarcoma presenting as retiform purpura during treatment of bullous pemphigoid

Kaposi sarcoma is a vascular neoplasm associated with human herpesvirus–8 and is most typically expressed in the skin. Disease presentations are currently grouped into 1 of 5 contextual types: classic, endemic, epidemic HIV-associated, nonepidemic and iatrogenic. The iatrogenic form is generally a consequence of transplantation-related immunosuppression; occurrence during immunosuppressive treatment of autoimmune disease is reported but unusual. Kaposi sarcoma may manifest clinically in a variety of guises, and at least 10 morphologies have been recognized: typical patch, plaque and nodular forms, and the more unusual lymphadenopathic, exophytic, infiltrative, ecchymotic, telangiectatic, keloidal, and cavernous/lymphangioma-like forms.1 Retiform purpura—branching and nonblanchable purple discoloration of the skin—is generally an indicator of vasculitis or vasculopathic occlusion, and has not been described as a manifestation of Kaposi sarcoma. We present an unusual case of Kaposi sarcoma manifesting as retiform purpura in the setting of bullous pemphigoid complicated by therapy-related leukopenia, which suggests that Kaposi sarcoma might be included in the differential diagnosis for retiform purpura.