S2708 Acute Peritonitis: A Case of Severe Inflammatory Bowel Disease Unmasked by Pregnancy

Abstract

Introduction: Rituximab (RTX) is a common therapy for several autoimmune and lymphoproliferative diseases, including hematologic malignancies. Development of autoimmune enterocolitis secondary to RTX is a rare but known adverse effect. The exact mechanism of pathogenesis is not completely understood. Case Description/Methods: A 60-year-old woman with history of non-Hodgkin lymphoma in complete remission, on maintenance RTX therapy for 2.5 years, was referred to gastroenterology for 3 months of early satiety, abdominal pain, vomiting, constipation, and diarrhea. Symptoms occurred daily and were accompanied by 12 pounds of unintentional weight loss over this period. She had no preceding gastrointestinal disease. Colonoscopy revealed abnormal thickening of the ileocecal valve and linear ulceration in the terminal ileum (TI) that could not be traversed with the colonoscope. Colonoscopy was repeated 1 month later along with MRE, both redemonstrating inflammation of the TI. She was diagnosed with Crohn's disease based on endoscopic and radiographic findings, elevated fecal calprotectin, and symptoms. She was induced on budesonide therapy with good response, then transitioned to vedolizumab, with improvement in symptoms. Due to her atypical age of presentation, development of Crohn's disease was associated with her chronic RTX exposure. Discussion: There have been few documented cases of RTX induced Crohn's disease, with most involving elderly patients on maintenance RTX therapy. Although not completely understood, it is suggested that the CD201 lymphocytes, which are reduced by RTX, must play a role in the pro and anti-inflammatory equilibrium within the gastrointestinal mucosa. The depletion of B regulatory cells which secrete antiinflammatory interleukin-10 is likely of particular importance in promoting a pro-inflammatory state. This case highlights a rare adverse effect of RTX in a patient who otherwise did not have any clear risk factors for developing inflammatory bowel disease. It is important to be aware of the possibility of Crohn's disease in a patient presenting with classical symptoms such as diarrhea, abdominal pain, and weight loss when on RTX therapy.