The common MTHFR deficiencies are usually asymptomatic, although the 677T variant can cause a mildly increased risk of some diseases. For individuals homozygous in the 677T variant, there is a mildly elevated risk of thromboembolism (odds ratio 1.2), and stroke (odds ratio 1.26). There is also an elevated risk of neural tube defects among children of individuals with the C677T polymorphism (odds ratio 1.38). For cardiovascular risk, common MTHFR deficiencies were once thought to be associated but meta-analyses indicate that correlation this was an artifact of publication bias.
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