Mutations C677T and A1298C of the 5,10-methylenetetrahydrofolate reductase gene and fasting plasma homocysteine levels are not associated with the increased risk of venous thromboembolic disease.

Mild hyperhomocysteinemia is associated with homozygosity for the thermolabile variant of 5,10-methylenetetrahydrofolate reductase (MTHFR) and could increase the risk of venous thromboembolic disease (VTD). Recently, the second A1298C mutation of the MTHFR gene was described. The present study aimed to analyze both mutations of the MTHFR gene and plasma homocysteine levels in subjects with VTD. The study groups comprised 146 patients with VTD and 100 healthy subjects. There were no statistical differences in carrier frequency and allelic frequency for both A1298C and C677T mutations, nor were there any differences encountered between subjects with VTD and controls in either plasma homocysteine levels or according to C677T or A1298C genotypes of MTHFR. In our VTD patients and controls, neither MTHFR 677CT/1298CC nor MTHFR 677TT/1298CC combined genotypes were observed; double heterozygotes (A1298C/C677T) were represented only in 11% of VTD patients, and in 15% of the controls. In conclusion, the polymorphisms C677T and A1298C of MTHFR and fasting plasma homocysteine levels do not seem to be significant risk factors for venous thromboembolic disease.