Etiology and assessment of hypercoagulability with lessons from heparin-induced thrombocytopenia.

Hypercoagulability, or thrombophilia, is a condition associated with an abnormally increased tendency toward blood clotting. Affected individuals are prone to developing venous or arterial thrombosis and often require thromboprophylaxis. Hypercoagulability can be generally classified as either an inherited or acquired condition. Patients with an inherited thrombophilia have genetic variances that alter the quality or quantity of proteins involved with hemostasis. Hypercoagulability may also be acquired and develop as an exaggeration of normal physiologic responses to major tissue injury, or an abnormal response to various prothrombotic clinical factors. Careful assessment for hypercoagulability is important because effective management strategies, often involving anticoagulation, may be available. Heparin-induced thrombocytopenia is an example of an acquired hypercoagulable state that has been well studied and, when recognized, responds to appropriate therapy. In this article, we review the etiology, risks, and assessment of thrombophilia, with emphasis on the clinical lessons learned from heparin-induced thrombocytopenia.