MTHFR and hyperhomocysteinemia: Mutations in some key genes encoding homocysteine-metabolizing enzymes, such as methylenetetrahydrofolate reductase (MTHFR) C677T and A1298C and methionine synthase reductase (MTRR) A66G, may contribute to the risk of the development of hyperhomocysteinemia and thus leas to clinical disorders [6].