[Discovery and prospects of a novel thrombophilia: antithrombin resistance]

Pathogenesis of venous thromboembolism (VTE) known to be complex and multifactorial process involves the interaction of acquired factors and genetic predisposing conditions. Deficiency of natural anticoagulant factors such as antithrombin (AT), protein C and protein S increases the risk of a VTE. Recently, we have reported novel mechanism of hereditary thrombosis in a Japanese family, in which AT resistance was associated with a missense mutation (p.Arg596Leu) in the prothrombin gene named prothrombin Yukuhashi. The mutant thrombin showed a low clotting activity, but a severely impaired inactivation by AT, resulting in a susceptibility to thrombosis. We have developed a new laboratory test to evaluate AT resistance in plasma. Prothrombin mutation causing AT resistance has found in Caucasian, not only in Japanese.