A second mutation in the methylenetetrahydrofolate reductase gene and the risk of venous thrombotic disease

We assessed the effect of a recently described mutation in the MTHFR gene (1298 A → C) on the risk of deep venous thrombosis (DVT) by determining its prevalence in 190 patients with verified DVT and in age-, race- and gender-matched controls. MTHFR 1298 A → C was found in 42.1% of patients and in 41.1% of controls. The OR for venous thrombosis was 1.07 (95% CI 0.70–1.65) for heterozygotes and 0.83 (95% CI 0.33–2.08) for homozygotes. The OR for the factor V Leiden (FVL) mutation was 3.40 (95% CI 1.22–9.48), for FII 20210 G → A was 5.22 (95% CI 1.12–24.2) and for MTHFR 677 C → T, 1.24 (95% CI 0.82–1.87). No significant increased risk for venous thrombosis was found when MTHFR 1298 A → C was coinherited with FVL (OR 2.85, 95% CI 0.88–9.23), FII 20210 G → A (OR 7.19, 95% CI 0.87–59.4) or MTHFR 677 C → T (OR 1.44, 95% CI 0.71–2.92). These data do not support a critical role of MTHFR 1298 A → C in the predisposition to DVT.