Description
Homocysteine is an amino acid derived from methionine. The levels are affected by physiological and pathological factors including deficiencies of vitamins B6,B12 and folate. Patients with classical homocystinuria are at high risk of vascular disease and accumulating data indicates that moderate elevations in plasma homocysteine are an independent risk factor for venous and arterial thrombotic disease in otherwise healthy individuals. A common mutation in the gene for methylenetetrahydrofolate reductase is present in the homozygous form in 12% of healthy individuals and in a heterozygous form in 40-45%. Individuals with the mutation have higher plasma homocysteine levels than those with the wild type genotype and in addition have higher homocysteine levels in the presence of low folic acid levels. There appears to be a correlation between MTHFR genotype and arterial thrombosis but the association with venous thromboembolic disease is less clear. Plasma homocysteine levels may be reduced by a combination of folate, B12 and B6 supplementation although further studies are required to determine whether this affects the clinical outcome.
