Mild hyperhomocysteinemia caused by MTHFR deficiency is a mild condition that may be associated with a slightly higher risk of neural tube defects and, in a small portion of individuals, pregnancy loss. However, for the vast majority, it causes no problems with their health or the health of their children. (The mild MTHFR deficiency for which Counsyl tests should not be confused with severe MTHFR deficiency.)
The MTHFR enzyme is involved in the conversion of the amino acid homocysteine to another amino acid, methionine. People with mild hyperhomocysteinemia caused by MTHFR deficiency may have a decreased ability to perform this conversion, and as a result they may have higher levels of homocysteine in their body and lower levels of the vitamin folate.
There are two common mutations found in the MTHFR gene, A222V and E429A (also known as C677T and A1298C, respectively). Having one copy of either mutation (being a carrier) is not thought to have any impact on one’s health or that of one’s children.
The following gene combinations may be significant. Note that they are only significant if they raise the level of homocysteine in the blood, and this does not happen in everyone.
For women, two copies of the A222V mutation and an elevated homocysteine level have been associated with a 2 to 3-fold higher risk of having a child with neural tube defects such as spina bifida. This type of birth defect normally affects 1 in 1,000 births, so women with two A222V mutations and an elevated homocysteine level would face a 2 to 3 in 1,000 (0.2-0.3%) risk.
Individuals with two copies of the A222V mutation should talk with their physician regarding a reflex test to measure fasting homocysteine levels. If fasting homocysteine levels are normal, no change in the medical management is needed. If fasting homocysteine levels are elevated, the patient's physician may advise them to take a higher dose of folate supplements.
This mutation pairing has been suggested to share the same issues as described above for the A222V/A222V mutation pairing.
This mutation pairing is NOT associated with any elevated risks for health problems.
Though risks may vary by ethnicity, mild hyperhomocysteinemia caused by MTHFR deficiency is very common as approximately 30-40% of individuals are carriers of the condition and approximately 10-15% have the condition. However, not all individuals with a mild hyperhomocysteinemia caused by MTHFR deficiency exhibit symptoms or at risk for symptoms.
Most people with mild hyperhomocysteinemia caused by MTHFR deficiency require no treatment. All pregnant women are advised to take folic acid supplements before and during pregnancy to reduce the risk of birth defects by as much as 75% to 85%. Instead, methylfolate supplements are particularly important for women who have an elevated homocysteine level due to MTHFR deficiency.
Based on current scientific knowledge, most people with mild hyperhomocysteinemia caused by MTHFR deficiency will be completely unaffected by it. Women whose MTHFR mutations result in an elevated homocysteine level have a slightly elevated risk of having a child with neural tube defects (0.2-0.3% versus 0.1% in the general population).
Explanations of an extensive number of genetic diseases written for everyday people by the U.S. government's National Institutes of Health.
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