Gastrointestinal lymphoma in a patient on long-term azathioprine therapy: A case report with imaging features mimicking Crohn's disease.

A 43-year-old female was admitted with a 1-month history of recurrent periumbilical abdominal pain and nausea. The patient had a 7-year history of Azathioprine use for the management of myasthenia gravis with AChR antibodies. The initial abdominal ultrasound revealed thickened small bowel walls at multiple sites. Abdominal CT enterography (CTE) raised suspicion for Crohn's disease or lymphoma. Upper gastrointestinal endoscopy revealed multiple ulcers in the gastric body and antrum, with biopsy samples taken from the lesions. Histopathological analysis confirmed a diagnosis of B-cell lymphoma in the stomach. However, the imaging characteristics of the small bowel lesions on CTE were inconclusive in distinguishing between Crohn's disease and lymphoma. After a multidisciplinary discussion, the patient was indicated for chemotherapy based on the confirmed diagnosis of gastric lymphoma. While awaiting the scheduled chemotherapy session, the patient developed sudden right iliac fossa pain, which subsequently spread across the abdomen. CT imaging revealed a perforation of the small intestine in the right iliac fossa. The patient underwent surgical resection of the affected small bowel segment, and pathological examination confirmed B-cell lymphoma in the small intestine.