Abstract
A 77-year-old woman with a history of endovascular aneurysm repair (EVAR) for an abdominal aortic aneurysm (AAA) presented with melena. She had been recently diagnosed with IgG4-related periaortitis and started on prednisone. Physical examination revealed pallor conjunctiva and melena on the rectal examination, with laboratory results indicating anemia (hemoglobin: 7.4 g/dl). Abdominal CT showed air within the aneurysmal sac, and endoscopy confirmed an aortoduodenal fistula. The patient underwent urgent stent removal, vessel replacement, and duodenal repair. She recovered well and was discharged on day 30 with ongoing prednisone therapy. The risk of fistula formation in IgG4-related periaortitis necessitates careful monitoring, especially in patients with pre-existing aortic pathology.