Hypercoagulable states.

A hypercoagulable state is an enhanced tendency to form venous or arterial thrombi. In 1845, Virchow postulated three factors responsible for thrombosis that remain relevant today: alterations of the blood (hypercoagulability); changes in vessel wall (vascular injury); and impairment of blood flow (stasis). An increased understanding of the molecular basis of thrombosis has been aided by the identification of individuals with specific inherited defects in the natural anticoagulation system. These primary hypercoagulable states include antithrombin III, protein C and protein S deficiencies, dysfibrinogenemias, plasminogen deficiency, and decreased plasminogen activator activity. Individuals with thrombosis at an early age, a family history of thromboembolic disease, unusual sites of thrombosis, or recurrent thrombosis without apparent cause should be evaluated for a primary hypercoagulable defect. The majority of patients do not have a recognizable specific defect. However, there are a variety of underlying conditions or diseases that are associated with an increased risk for thrombosis. The etiologies of secondary hypercoagulable states are often unclear and may be multifactorial. Treatment of these inciting conditions or diseases may decrease the thrombotic tendency.