2022 Volume 64 Issue 8 Pages 1469-1474
A 67-year-old man with rheumatoid arthritis presented with abdominal pain, diarrhea, and rectal bleeding 4 months after administration of abatacept (a recombinant fusion protein comprising a fragment of the Fc domain of human immunoglobulin G1 and the extracellular domain of human cytotoxic T-lymphocyte antigen 4). Colonoscopy revealed diffuse colitis mimicking ulcerative colitis. Other areas of the gastrointestinal tract were unaffected. We diagnosed the patient with abatacept-induced immune-mediated adverse event. Administration of prednisolone led to improvement in symptoms. Although rare, immune-mediated colitis should be considered in the differential diagnosis of patients with diarrhea or rectal bleeding observed during abatacept therapy.
