Abstract
<title>Abstract</title> <p>Background: Pyoderma gangrenosum is a rare neutrophilic dermatosis that can complicate Behçet disease. The simultaneous presentation of catastrophic multisite thrombosis and pyoderma gangrenosum as initial manifestations of Behçet disease is exceptionally rare. This case describes a young male with previously undiagnosed Behçet disease presenting with this unusual combination. Case presentation: A 19-year-old man presented with painful necrotic leg ulcers evolving over 40 days. He later developed fever, cough, hemoptysis, and progressive thrombosis despite therapeutic anticoagulation. Thrombosis involved deep veins, mesenteric vein, and hepatic artery. Oral aphthae appeared on day 16 of hospitalization. Autoimmune and thrombophilia workups were negative including antiphospholipid antibodies. A clinical diagnosis of Behçet disease was established. The patient received pulse methylprednisolone, nine plasma exchange sessions, and cyclophosphamide. His ulcers healed completely after six cyclophosphamide cycles with no recurrence at follow-up. Conclusions: This case presents a rare instance of pyoderma gangrenosum as the initial manifestation of Behçet disease with catastrophic multisite thrombosis. Negative antiphospholipid antibodies distinguished this presentation from catastrophic antiphospholipid syndrome. This case raises the possibility that pyoderma gangrenosum in Behçet disease may associate with a more severe thrombotic phenotype. Further studies are needed to determine this association, especially in the absence of classic mucocutaneous manifestations at presentation.</p>