Increased Factor V Leiden frequency is associated with venous thrombotic events among young Brazilian patients

Of the inherited thrombophilias, the Factor V Leiden (FVL) and the prothrombin mutant (FII G20210A) are associated with increased risk of venous thromboembolism (VTE). The C677T mutation of the methylenetetrahydrofolate reductase gene, which may lead to hyperhomocysteinemia, is also considered a risk factor for VTE in some studies. However, the frequency of these genetic risk factors may vary significantly among different populations.

The FVL, FII G20210A and C677T mutations were investigated by PCR-RFLP in 275 young VTE Brazilian patients as well as in 324 biologically unrelated individuals selected to compose the control group.

The C677T mutation in the MTHFR gene was detected in 135 (49.1%) patients, of which 117 (42.5%) were identified as heterozygous and 18 (6.5%) as homozygous. The G20210A mutation was detected in 14 (5.1%) patients in heterozygosis. In both cases, no significant difference was observed when these results were compared to the frequencies observed in the control group. FVL was detected in heterozygosis in 19 (6.9%) patients, corresponding to a significantly increased frequency when compared to that observed for the control group (1.2%) (OR 5.9; 95% CI 2.08-16.79; p < 0.001).

The data indicated that FVL is significantly associated with VTE among young Brazilian patients, but also supported previous evidence that VTE is a multi-factorial disease, resulting from the interaction of genetic and acquired risk factors.