MTHFR and hyperhomocysteinemia: Hyperhomocysteinemia (HH) may be due to a genetic defect in the MTHFR, cystathionine synthase or methyltetrahydrofolate homocysteine methyltransferase enzymes, to an acquired nutritional deficiency in vitamin cofactors (folic acid, vitamins B6 and B12)13, to a chronic medical condition or to adverse drug effect14,15.