TB or not to be: A case of atypical gastrointestinal tuberculosis mimicking Crohn’s disease – A case report

Gastrointestinal tuberculosis (GI TB) is a rare form of extrapulmonary TB that often mimics Crohn’s disease (CD) due to overlapping clinical, endoscopic, and histopathologic features. We present a case of GI TB that initially manifested as a perianal fistula, an atypical presentation for TB but commonly seen in CD. Familiarity with this presentation is essential to ensure timely diagnosis and appropriate management, particularly in TB endemic regions. A 38-year-old male from the Philippines presented with a 4-year history of chronic perianal fistula and recurrent rectal pain, initially diagnosed as CD based on findings from three colonoscopies and biopsies showing non-caseating granulomas. MTB GeneXpert and mycobacterial cultures were consistently negative. He was treated with antibiotics, corticosteroids, and biologic therapy, but showed no clinical improvement. One month later, he returned with persistent symptoms and sudden onset jaundice, accompanied by marked elevation of liver enzymes. Imaging revealed hepatosplenomegaly, hepatic nodules, and lymphadenopathy. A fourth colonoscopy with biopsy demonstrated caseating granulomas and Langhans giant cells, confirming tuberculous ileitis. Anti-tuberculosis therapy was initiated, resulting in significant clinical and biochemical improvement, including normalization of liver enzymes and closure of the perianal fistulas. This case highlights the diagnostic challenge of distinguishing GI TB from Crohn’s disease in TB endemic regions. A high index of suspicion for TB must be maintained before initiating biologic therapy. Histopathologic confirmation and careful clinical correlation are essential for accurate diagnosis and appropriate treatment. • Gastrointestinal tuberculosis (GI TB) may mimic Crohn’s disease, complicating diagnosis. • Perianal fistula can be a rare initial manifestation of GI TB in TB-endemic regions. • Negative GeneXpert and cultures do not exclude intestinal tuberculosis. • Immunosuppressive therapy may worsen undiagnosed TB and lead to dissemination. • Multidisciplinary evaluation and repeated biopsies improve diagnostic accuracy.