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Methylene tetrahydrofolate reductase is an enzyme involved directly, and indirectly, in folate and homocysteine metabolism. The (thermolabile) c.677C>T MTHFR polymorphism is present in the homozygous form in 5-15% of the general population. Individuals who are homozygous for the c.677C>T MTHFR variant may have mild elevations in blood homocysteine levels, especially in the setting of inadequate folate intake. Elevated homocysteine is an independent risk factor for venous thromboembolism. Approximately 20% of the population are compound heterozygotes for both MTHFR polymorphisms. Less is known about the thrombotic risk associated with 1298 A>C. The presence of other predisposing risk factors for thrombosis in addition to elevated homocysteine is considered synergistic.
The c.677C>T variant is also associated with methotrexate toxicity.
Seattle Children’s provides healthcare for the special needs of children regardless
of race, sex, creed, ethnicity or disability. Financial assistance for medically
necessary services is based on family income and hospital resources and is provided
to children under age 21 whose primary residence is in Washington, Alaska, Montana
Seattle Children’s Hospital, Research