Although the relative risk of VTE is very significantly increased in factor V Leiden positive women using contraceptive pills, the absolute incidence of venous thrombotic events is low and fatal pulmonary embolism is rare.
Factor V Leiden (Arg506Gln), a confounding genetic risk factor but not mandatory for the occurrence of venous thromboembolism in homozygotes and obligate heterozygotes for cystathionine beta-synthase deficiency.
The incidence of venous thromboembolism in carriers of the prothrombin gene mutation is slightly lower than that observed in carriers of factor V Leiden, whereas in carriers of both mutations it is two or three times higher.
The genetic defect of coagulation factor V known as factor V Leiden produces a resistance to degradation by activated protein C (APC) and increases the risk of venous thromboembolism.
The relatively low incidence of venous thromboembolism in the Chinese population compared with Caucasians is probably as a result of the low prevalence of factor V Leiden or other environmental or genetic factors.
We have analyzed 5971 control individuals originating from 26 geographically defined populations in Europe and neighboring countries for the presence of factor V Leiden, an important genetic risk factor in venous thromboembolism.
High frequency of association between both mutations supports the need to perform simultaneous genetic analyses of factor V Leiden and PT20210A in all VTE patients.
A total of 218 men with incident venous thromboembolism were genotyped for the prothrombin mutation and for factor V Leiden and were followed prospectively for recurrent VTE over a follow-up period of 7.3 years.
Carriers of a double thrombophilic mutation (factor V Leiden and prothrombin G20210A) are at high risk of a recurrent venous thromboembolism (VTE), and may benefit from a longer course of secondary prophylaxis.
Factor V Leiden (FVL)-carrying relatives of selected patients with venous thromboembolism (VTE) have much higher venous thrombotic risks than FVL-carrying relatives of unselected consecutive patients with VTE.
Multivariate analysis showed a small, non-significant additional effect of the prothrombin mutation on the risk of venous thromboembolism in heterozygotes for factor V Leiden [adjusted hazard ratio, 1.3; 95% confidence interval (CI), 0.5-3.8].
Little conclusive information is available on the actual risk of venous thromboembolism during pregnancy or puerperium in women with inherited thrombophilia, particularly in carriers of factor V Leiden and of the G20210A prothrombin gene mutation.
The activated protein C (APC) resistance phenotype associated with an abnormal factor V Leiden (FVL), and the G20210A prothrombin gene mutation are the most common findings in patients with venous thromboembolism (VTE).