Immuno-mediated colitis induced by nivolumab that mimics endoscopically and histologically an ulcerative colitis

Immunotherapy has revolutionized the management of oncological pathology, demonstrating effectiveness in treating various cancers by stimulating the immune system against tumor cells. Among the immunotherapy drugs are programmed cell death protein 1 (PD-1) inhibitors, such as Nivolumab, which, by blocking this receptor on the surface of T lymphocytes, enhance the immune response. Despite their significant benefits, these agents present specific adverse effects on healthy tissues that need to be understood. One of these effects is immune-mediated colitis, a potentially serious gastrointestinal disorder that may require the permanent discontinuation of the drug. Although it can occur with various immunotherapy regimens, it occurs more frequently with anti-CTLA4 agents like Ipilimumab, with its incidence much lower with anti-PD1 agents. We present the case of a 62-year-old male diagnosed with metastatic clear cell renal carcinoma treated with radical nephrectomy and subsequent palliative systemic treatment with Nivolumab. After the third cycle of immunotherapy, he developed abdominal pain and diarrhea. Colonoscopy revealed continuous mucosal inflammation up to the cecum, erosions, exudates, and loss of the vascular pattern. Biopsies showed signs of active colitis, cryptic abscesses, and focal cryptitis, all consistent with a case of immuno-mediated colitis induced by Nivolumab that mimics, both endoscopically and histologically, the findings found in ulcerative colitis.