Factor V Leiden: how great is the risk of venous thromboembolism?

The factor V Leiden mutation, the most common inherited cause of thrombophilia, causes a mild hypercoagulable state. We describe a 29-year-old man, heterozygous for factor V Leiden, who developed extensive pulmonary emboli with concomitant bilateral deep venous thrombosis, likely provoked by prolonged immobility during a car trip. We then review the diagnosis, therapy, screening, and prognosis of venous thromboembolism related to factor V Leiden.