Supplementary Material for: A Case Report: Cryptogenic Multifocal Ulcerative Stenosing Enteritis (CMUSE), A Diagnostic Challenge Mimicking Crohn’s Disease

Cryptogenic Multifocal Ulcerative Stenosing Enteritis (CMUSE) is a rare, underrecognized small bowel disorder that often mimics Crohn’s disease, leading to delays in diagnosis and misdirected treatment. We present the case of a 41-year-old male with chronic anemia, fatigue, weight loss, and intermittent abdominal pain with melena, who was followed for nine years before a definitive diagnosis was established. Despite extensive evaluations, including imaging and endoscopy, the cause of his symptoms remained elusive. Initial management with TNF inhibitors and IL-12/IL-23 blockade failed to provide sustained relief, and the patient required multiple surgical resections due to recurrent strictures. Pathological examination consistently demonstrated multifocal jejunal ulceration with stenosis but lacked granulomas, vasculitis, or systemic inflammatory markers, ultimately confirming CMUSE. Given its relapsing nature and resistance to conventional inflammatory bowel disease therapies, CMUSE presents significant therapeutic challenges. The patient's ongoing management includes upadacitinib, a JAK1 inhibitor, which may modulate immune activation pathways contributing to ulcer formation and stricture development. This case underscores the need for increased clinical awareness of CMUSE, highlights the role of genetic testing in differentiating it from Crohn’s disease, and emphasizes the importance of further research to optimize treatment strategies for this rare condition.