Molecular genetic aspects of hyperhomocysteinemia and its relation to folic acid.

In a review of research by the author and her colleagues, the genetic basis of hyperhomocysteinemia and the relation between this condition and plasma folate levels are elucidated. There has recently been renewed interest in homocysteine metabolism because hyperhomocysteinemia has been associated with occlusive arterial disease and neural tube defects. The article focuses on a critical enzyme of folate metabolism, 5,10-methylenetetrahydrofolate reductase. A deficiency of this enzyme results in hyperhomocysteinemia and a wide variety of neurologic and vascular symptoms. Molecular genetic analysis of the enzyme has led to the identification of nine rare mutations associated with a severe-deficiency phenotype as well as one common mutation (found in 35% to 40% of alleles in the general population) that is proposed as a risk factor in some forms of cardiovascular disease and in neural tube defects.