Question: A 54-year-old white man with a history of infection with human immunodeficiency virus complicated with disseminated bartonellosis infection was recently diagnosed with multicentric Castleman disease. He was treated with 4 weekly doses of rituximab 375 mg/m2 and methylprednisone 4 mg/d. His further treatment consisted of ritonavir boosted daranuvir, emtricitabin, and tenofovir. His CD4 count was 100/μL, and his viral load 151 copies/mL. During his second course of chemotherapy, he developed complaints of anal pain and rectal bleeding.