Antithrombin defi ciency with portal vein thrombosis is an unusual disease in clinic. A 16-year-old adolescent with a history of frequent spontaneous epistaxis and hypersplenism in his childhood presented with abdominal pain and distension. Chronic portal vein thrombosis, portal hypertension, and hypersplenism were caused by antithrombin defi ciency based on laboratory data and image fi ndings. He underwent splenectomy and subsequent anticoagulation therapy with warfarin. Postoperative course was uneventfully. During 1 year follow-up, he had no epistaxis and epigastric pain and platelet count showed normal value (366,000/μL)