Crohn's Disease Mimicking Behçet's Disease and Complicated by Colonic Perforation: A Case Report.

Behçet's disease and Crohn's disease share overlapping clinical features, including recurrent oral and genital ulcerations, arthralgias, and gastrointestinal inflammation, frequently leading to diagnostic uncertainty. Accurate differentiation is essential, as management strategies and long-term outcomes differ substantially. We report a diagnostically challenging case of a 60-year-old Hispanic male who initially presented with progressive weight loss, painful oral and genital ulcers, arthralgias, and chronic diarrhea and was treated for presumed Behçet's disease with corticosteroids and immunomodulatory therapy, resulting in partial symptomatic improvement. Despite treatment, his condition deteriorated over several months, culminating in severe abdominal pain and bowel perforation. Computed tomography (CT) revealed pneumoperitoneum and sigmoid wall thickening, prompting emergent exploratory laparotomy with Hartmann's procedure for feculent peritonitis. Histopathologic examination demonstrated multifocal ulceration with transmural mixed inflammation and serositis without evidence of vasculitis or granuloma formation, representing the key diagnostic turning point and confirming Crohn's disease over intestinal Behçet's disease. Postoperatively, surgical pathology confirmed a diagnosis of Crohn's colitis, for which he was initiated on infliximab with subsequent clinical stabilization. This case highlights the diagnostic challenges posed by overlapping mucocutaneous and gastrointestinal manifestations, underscores the importance of early histologic confirmation and multidisciplinary evaluation, and emphasizes the need for ongoing diagnostic reassessment to prevent catastrophic complications in patients with systemic inflammatory presentations.