Factor V Leiden Mutation
and Prothrombin Mutation G20210A
Venous thrombosis is a multifactorial disorder, involving one or a combination of genetic and acquired risk factors. Known genetic causes are present in approximately 25% of unselected venous thrombosis cases and up to 63% of familial cases. Factor V Leiden Mutation is the most common genetic risk factor for venous thrombosis.
· Who should be tested for factor V leiden mutation?
Age <50, any venous thrombosis
Venous thrombosis in unusual sites (such as hepatic, mesenteric, and cerebral veins).
Recurrent venous thrombosis.
Venous thrombosis and a strong family history of thrombotic disease.
Venous thrombosis in pregnant women or women taking oral contraceptives.
Relatives of individuals with venous thrombosis under age 50.
Myocardial infarction in female smokers under age 50.
Women with recurrent pregnancy loss or unexplained severe pre-eclampsia, placental abruption, intrauterine fetal growth retardation or stillbirth. Knowledge of factor V leiden carrier status may influence management of future pregnancies.
· Should patients found to be positive for factor V Leiden mutation be tested for any of the other heritable thrombophilic risk factors?
Venous thrombosis is multifactorial, and the presence of more than one genetic risk factor is not uncommon. After factor V leiden, the most common are the prothrombin mutation G20210A and hyperhomocysteinemia.
Hyperhomocysteinemia should be tested in most cases by measuring plasma homocysteine levels and methylenetetrahydrofolate reductase (MTHFR) gene mutation which accounts for certain cases of hyperhomocysteinemia.
Hyperhomocysteinemia interacts synergistically with coexisting factor V leiden to increase the relative risk of venous thrombosis to 20-fold greater than in individuals without either risk factor.
Identification of Factor V, Prothrombin and MTHFR gene mutations by Multiplex PCR and Reverse Hybridization is done in 48 hours, in Saridar Lab.