The MTHFR gene provides instructions for making an enzyme called methylenetetrahydrofolate reductase, which plays a role in processing folate and homocysteine in the body. An MTHFR mutation is a change in the DNA sequence of the MTHFR gene that affects the activity of the enzyme it produces. The most common MTHFR mutation is the MTHFR C677T variant, which may also be referred to as MTHFR 677 C>T or MTHFR 677 C→T. Each person has two copies of the MTHFR gene, and there are three possible genotypes: MTHFR 677 CC, MTHFR 677 CT, and MTHFR 677 TT.
MTHFR mutations can lead to high levels of homocysteine in the blood, which may contribute to several health conditions, including birth anomalies, glaucoma, certain mental health conditions, and certain types of cancer. However, most people with MTHFR gene polymorphisms do not have neural tube defects, nor do their children. Symptoms of MTHFR mutations vary among individuals and depend on the type of mutation they have, and people usually do not know they have an MTHFR mutation unless they undergo genetic testing or have a health issue.
The MTHFR mutation test detects two of the most common mutations in the MTHFR gene that are associated with elevated levels of homocysteine in the blood. It may be ordered when a person has elevated homocysteine levels, especially when the person has a personal or family history of premature cardiovascular disease or thrombosis. However, it is not routinely ordered, and some laboratories and organizations recommend against using it for thrombophilia screening.
