Abstract
A 19-year-old man was referred due to sudden onset of right foot pain and chest discomfort. Contrast-enhanced computed tomography revealed massive thrombi in the right pulmonary artery and femoral vein. The patient's father had experienced multiple recurrences of venous thromboembolism (VTE) and was diagnosed with inherited antithrombin deficiency by a genetic examination. The patient was administered the oral factor Xa inhibitor rivaroxaban (30 mg). After seven days, the thrombus disappeared. Rivaroxaban (15 mg) was continued for 6 months with no recurrence, indicating the efficacy of this factor Xa inhibitor for the treatment and prevention of VTE in patients with antithrombin deficiency.