Extensive cutaneous iatrogenic Kaposi's sarcoma after bullous pemphigoid treatment with oral methylprednisolone: a rare Chinese case report.

Bullous pemphigoid (BP) is an autoimmune disease that requires immunosuppressive therapy. Systemic corticosteroids are considered the standard treatment for moderate-to-severe BP. Kaposi's sarcoma (KS) is a rare multifocal endothelial tumour that affects the skin, mucosa and viscera. As an angioproliferative disease of obscure aetiopathogenesis and histogenesis, KS is associated with human herpesvirus 8 (HHV-8). This current case report describes a rare occurrence of extensive cutaneous KS in a 60-year-old Chinese male patient after oral methylprednisolone treatment for BP with an emphasis on its pathological characterization. A total of more than 40 nodules were found on his trunk and lower limbs covering more than 20% of his body surface area. Immunohistochemical staining of biopsy samples from the lesion showed the patient was positive for HHV-8, CD31, CD34, XIIIa, ERG and Ki-67. The Epstein-Barr virus test showed the patient tested negative for immunoglobulin (Ig)A and IgM, but was positive for IgG. Immunosuppression associated with the treatment for BP may activate a latent HHV-8 infection and induce the development of KS.