Thrombophilia: How To Test? How To Manage?

By Julie Hambleton, MD

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Prothrombin 20210

The prothrombin gene mutation is the second most common genetic predisposition to thrombosis in the Caucasian population. It is characterized by a G-to-A transition in the 3'-untranslated region of the prothrombin (factor II) gene. This mutation is associated with mild increases in plasma prothrombin levels and thus with an increased risk of venous thrombosis. In one study, the FII 20210A polymorphism was found in 18% of selected patients with a personal and family history of venous thrombosis, in 6.2% of unselected consecutive patients presenting with their first unprovoked DVT, and in 2.3% of normal control subjects. As with the factor V Leiden mutation, the prothrombin mutation is relatively rare in African-American and Asian populations. Heterozygotes of the 20210A allele have a three- to fourfold increased risk of VTE, which is further increased by the use of estrogen therapy, pregnancy, and the concomitant presence of the factor V Leiden mutation.

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