Apart from MTHFR defects, hyperhomocysteinemia may be possibly caused by diseases such as nephropathy14, psoriasis15, hypothyroidism16, diet problems such as vitamin B12 deficiency, folate deficiency, alcoholism, high intake of methionine17 and medication such as nitrous oxide inhalation18,19. The gene discussed is MTHFR; the disease is hyperhomocysteinemia.