Nutritional deficiency of folic acid and vitamin B6 and/or B12 and renal insufficiency often cause relatively mild hyperhomocysteinemia, while genetic disorders such as mutations in N-5,10-methylenetetrahydrofolate reductase (MTHFR) and CBS may result in moderate and severe hyperhomocysteinemia [17, 18]. Here, CBS is linked to hyperhomocysteinemia.