The MTHFR gene provides instructions to the body about how to make methylenetetrahydrolfolate reductase, a vitamin dependent enzyme. Three different SNPs (single nucleotide polymorphism) can combine in individuals, causing mutations of this gene. These mutations can affect how well an individual absorbs the B vitamin folate. Specific SNP combinations for MTHFR can also increase risk for neural tube defects in babies (except in Dutch and Irish populations), those with homocystinuria, and is suspected to increase risk factors for hypertension, stroke, heart disease, preeclampsia, glaucoma, cleft lip and plate, psychiatric disorders, and certain types of cancer. Knowing MTHFR SNP combinations is useful to healthcare practitioners when planning effective treatment.
Source: SNPedia (https://www.snpedia.com/index.php/MTHFR)