Endoscopic and Histopathologic Findings of Rituximab-Associated Colitis in a Patient With Scleroderma.

Rituximab is a chimeric monoclonal antibody that targets the CD20 antigen found on B lymphocytes. It is widely used in the treatment of haematological malignancies and, more recently, autoimmune diseases such as rheumatoid arthritis and scleroderma. While its safety profile is generally considered to be acceptable, a range of gastrointestinal adverse effects have been reported, including colitis. While this event is uncommon, there is a documented association with the development of de novo inflammatory bowel disease, particularly in patients with no prior history of digestive pathology. The clinical manifestations may be subtle or overlap with symptoms commonly found in other autoimmune diseases, which makes diagnosis difficult and increases the risk of complications such as stenosis, haemorrhage, or perforation. We present the case of a patient with systemic sclerosis under chronic rituximab treatment who developed colitis with clinical, endoscopic, and histopathological features consistent with ulcerative colitis. This case highlights the need for clinicians to remain vigilant for persistent gastrointestinal symptoms in patients undergoing anti-CD20 therapy and underscores the importance of early endoscopic evaluation with biopsies for the prompt detection of such complications.