An improved method for the detection of the thermolabile variant of methylenetetrahydrofolate reductase

The thermolabile variant of the methylene tetrahydrofolate reductase (MTHFR) in the homozygous state has been shown to be responsible for mild hyperhomocystinemia, hypomethioninemia, and hyperhomocystinuria (1). This variant is responsible for an increased risk for recurrent early pregnancy loss and neural-tube defects (2)(3). The presence of hyperhomocystinemia is also predictive of both arterial and venous thromboembolic disease (4)(5)(6)(7) and is a risk factor for coronary artery stenosis, independent of other risk factors such as age, smoking, hypercholesterolemia, and hypertension (8). Four to 6% of the Caucasian population (9) and 13–20% of the thrombosis-prone patients are homozygous for the thermolabile variant of MTHFR, which is caused by a C-to-T substitution at nucleotide 677 of the cDNA, resulting in the substitution of a valine for an alanine (8). A simple molecular diagnosis is of particular interest because this risk factor is quite common, the biochemical assay requires a methionine load, and folate supplementation is likely to prevent some of the complications (10)(11). Thus, the exploration has been recommended in the management of premature venous and arterial occlusive diseases (4). We report here an improvement of the method described previously to assess the thermolabile variant of MTHFR, based on multiplex amplification of MTHFR …