Inherited thrombophilic states.

Thrombophilic states are a group of conditions associated with increased predisposition to thromboembolic events. The well-recognized inherited thrombophilic states include resistance to activated protein C (APC) (Factor V Leiden) and deficiencies of plasma antithrombin, protein C, and protein S. These entities are aberrations in the natural anticoagulant systems that exist in plasma and at the endothelial cell level. Other causes of inherited thrombophilia include hyperhomocysteinemia, abnormalities in the proteins of the fibrinolytic system, dysfibrinogenemias, deficiency of heparin cofactor II, abnormal thrombomodulin, and the recently described variation in the prothrombin gene. Most of the inherited abnormalities recognized to date are associated with venous thromboembolism (VTE) rather than arterial thrombosis. Approximately half of VTE episodes in patients with inherited thrombophilias occur in relation to events that are generally recognized as predisposing states, such as surgery, pregnancy, and immobilization. In this review, the risks of VTE associated with inherited risk factors are discussed, and guidelines for the diagnosis and management are presented.