F5 and Rare hereditary thrombophilia: The risk of thromboembolism is increased when heterozygous Factor V Leiden is combined with other heritable thrombophilias, with antiphospholipid antibodies, with clinical factors such as obstetric settings and surgery, and with drugs such as oral contraceptives [2] and likely with other factors that increase the risk for thromboembolism such as infections [3].