In homozygous condition, its decreased activity causes the development of mild hyperhomocysteinemia.6, 7Another common SNP is an A to C change in position 1298 (A1298C) at exon 7 causing a glutamate to alanine substitution on the 429th position, resulting in decreased MTHFR activity, which is not associated with thermolability of an enzyme. Here, MTHFR is linked to hyperhomocysteinemia.