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Genetic and Rare Diseases Information Center (GARD)

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MTHFR gene mutation


* Not a rare disease
Other Names for this Disease
  • Methylenetetrahydrofolate reductase mutation
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The MTHFR gene provides the instructions for making the MTHFR enzyme, which plays a role in converting the amino acid homocysteine to methionine. A change in a gene is called a mutation or a polymorphism. Some changes in the MTHFR gene are very common, such as the C677T mutation or the A1298C mutation. These mutations result in a version of the MTHFR enzyme that has a mildly to moderately reduced function. There are also rare mutations in the MTHFR gene that severely impair the enzyme and cause a rare disease called homocystinuria.[1] 

People with a personal or family history of heart disease or blood clots may be tested for the common MTHFR gene mutations. Because each person has two copies of the MTHFR gene, it is possible to have one or two MTHFR gene mutations. If you have two mutations, you are said to be homozygous. If you have one mutation, you are heterozygous. Individuals with two C677T mutations and people with one C677T and one A1298C mutation have an increased risk of developing blood clots. Having this increased risk does not mean that a person will develop a clot, as many people with MTHFR gene mutations never do.[1]
Last updated: 9/18/2012


  1. MTHFR. Lab Tests Online. September 6, 2011; Accessed 9/14/2012.
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Basic Information

In Depth Information

  • The Online Mendelian Inheritance in Man (OMIM) is an catalog of human genes and genetic disorders. Each entry has a summary of related medical articles. It is meant for health care professionals and researchers. OMIM is maintained by Johns Hopkins University School of Medicine. 
  • PubMed is a searchable database of medical literature and lists journal articles that discuss MTHFR gene mutation. Click on the link to view a sample search on this topic.