Aortic graft invasion into duodenum as an atypical pathergy phenomenon in vascular Behçet's disease.

Behçet's disease (BD) is a multisystemic inflammatory disorder that can affect vessels of all sizes, often leading to significant vascular morbidity. We present the case of a 37-year-old man with BD who developed a rare and severe postoperative complication involving vascular graft invasion into the duodenum. The patient initially underwent emergency aortobiiliac bypass surgery for a ruptured abdominal aortic aneurysm. Subsequent evaluation revealed clinical features consistent with BD, and immunosuppressive treatment with corticosteroids and azathioprine was initiated; however, adherence was interrupted due to repeated abdominal surgeries. On follow-up, he presented with lower-extremity ischemia and gastrointestinal bleeding. Imaging revealed a recurrent thrombotic event and, notably, a contrast-enhancing structure that raised suspicion of a vascular material. Endoscopic evaluation demonstrated vascular graft material protruding into the duodenal lumen with active bleeding. Urgent redo of aortobiiliac graft replacement and duodenal repair were performed. This complication was interpreted as a manifestation of an extended pathergy phenomenon, triggered by mechanical trauma from graft contact with the duodenum in the context of uncontrolled disease activity. Following postoperative stabilisation, intensified immunosuppressive therapy with azathioprine and infliximab was administered, thereby preventing further vascular events and other severe manifestations. This case underscores the critical importance of adequate immunosuppressive control before vascular surgery in BD to reduce severe postoperative complications.