Fecal zonulin in the differential diagnosis of intestinal tuberculosis and Crohn’s disease: a case report

Abstract Background This case report addresses the diagnostic challenge of distinguishing intestinal tuberculosis (ITB) from Crohn’s disease, with a focus on the potential role of fecal zonulin as a noninvasive biomarker. Case presentation A 43-year-old female with a history of deep vein thrombosis, asthma, and previously treated pulmonary tuberculosis presented with fatigue, chronic diarrhea, diffuse abdominal pain, significant weight loss (~ 20 kg), and anorexia. Laboratory findings included a positive fecal occult blood test and markedly elevated fecal calprotectin (3370 µg/g, normal range: < 50 μg/g). Celiac disease serologies were negative. Abdominopelvic tomography showed pathological thickening of the digestive tract wall. Fecal zonulin was normal (10.75 ng/mL, reference range < 107 ng/mL). Upper endoscopy revealed multiple gastric ulcers and an esophageal ulcer suggestive of tuberculosis. Despite clinical and biochemical features mimicking IBD, endoscopic findings and normal fecal zonulin levels prompted suspicion of gastrointestinal TB. The pulmonology department confirmed intestinal tuberculosis and reactivation of the pulmonary tuberculosis after microscopic examination of the patient’s sputum and fecal samples. Antituberculous therapy was initiated with favorable evolution. Conclusion This case highlights the diagnostic overlap between ITB and Crohn’s disease and underlines the importance of integrating clinical history, imaging, and biomarkers. Fecal zonulin may aid in differentiating ITB from Crohn’s disease by reflecting intestinal permeability patterns, potentially preventing misdiagnosis and inappropriate immunosuppressive treatment. As a biomarker reflecting intestinal barrier integrity, fecal zonulin measurement may have broader implications that warrant further investigation.