Prothrombin G20210A mutation, antithrombin, heparin cofactor II, protein C, and protein S defects

The defects described in this article are not as common as factor V Leiden, but they are more common than many other hereditary procoagulant defects. The incidence of the prothrombin gene (G20210A) mutation is not yet known with certainty, but it may approach or even exceed that of factor V Leiden. These defects also seem less common than hereditary sticky platelet syndrome; however, they always should be considered in any individual with unexplained thrombosis and should be part of the work-up for patients with thrombotic disorders. Of the defects discussed, prothrombin G20210A mutation seems to be more common than antithrombin, protein C, protein S, or heparin cofactor II defects. Assessment of prothrombin gene mutation should be part of the primary evaluation of patients with unexplained thrombosis.