Abstract
We herein report a patient with a history of rheumatoid arthritis treated with methotrexate, which caused methotrexate-associated lymphoproliferative disorder and obstructive jaundice due to an enlarged lymph node. The obstructive jaundice was treated with endoscopic biliary stenting. A histopathological examination revealed features of Hodgkin's lymphoma, and chemotherapy with brentuximab vedotin was administered. Cholangiography and duodenoscopy after four rounds of chemotherapy revealed a choledochoduodenal fistula that developed in response to chemotherapy. It should be noted that, in cases of lymphoma infiltrating the gastrointestinal wall, fistulae can occur because of rapid regression due to regimens comprising monoclonal antibodies, such as rituximab and brentuximab vedotin.