The prevalence of 677T homozygosity varies with race. 18-21% of Hispanics and Southern Mediterranean populations have this variant, as do 6-14% of North American Whites and <2% of Blacks living outside of Africa. The prevalence of the 1298C mutation is lower, at 4-12% for most tested populations. A study in 2000 had identified only 24 cases of severe MTHFR deficiency (from nonsense mutations) across the whole world.
Methylenetetrahydrofolate reductase deficiency
Dihydrofolate reductase deficiency
Adenine phosphoribosyltransferase deficiency
Guanidinoacetate methyltransferase deficiency
5,10-methenyltetrahydrofolate synthetase deficiency
Purine nucleoside phosphorylase deficiency
Dihydropyrimidine dehydrogenase deficiency
Adenosine deaminase 2 deficiency