Thrombophilia and hypercoagulability.

This is a review of less well-known aspects of thrombophilia and hypercoagulability as they relate to thrombosis. Thrombosis is an abnormal fibrin clot that develops in circulating blood with clinical symptoms of one or more arterial and/or venous obstructions exclusively identified by imaging techniques. The terms thrombophilia and hypercoagulability are often used indiscriminately when they are in fact separate entities. Thrombophilia is an inherited or acquired clinical phenotype manifesting in selected individuals as a greater risk to develop recurrent thrombosis at a younger age than the general population, with considerable differences in the magnitude of risks among individuals in the same family with the same thrombophilic gene defect. Hypercoagulability is a laboratory phenotype whereby in vivo activation of clotting, fibrinolysis, endothelial cells and platelets is identified in vitro by specialized clotting techniques and by specific antibodies directed at biomarkers of clotting activation and damaged vasculature. Hypercoagulability may be provoked by drugs to treat bleeding in hemophilia, by sepsis, inflammation, surgery, blood stasis, atherosclerosis, and it manifests selectively in inherited and acquired thrombophilia. A chronology of the discovery of acquired and inherited thrombophilia puts in perspective the data analyzed in two representative large family studies that address whether venous and arterial thrombosis are a necessary outcome in thrombophilia, and the question, whether patients with inherited antithrombin, protein C and protein S deficiencies need to be treated after a first episode of thrombosis. The liberal use of case vignettes emphasizes a close relationship and the distinction between thrombosis, thrombophilia and hypercoagulability.