Skip to main content
Factor V Leiden, MTHFR Thermolabile Variants, Prothrombin 20210G>A. The factor V Leiden mutation is the most common cause of activated protein C (APC) resistance, and most common genetic risk factor for thrombosis. Approximately 3-8% of the population is heterozygous, and have an estimated 5-10 fold increased risk of thrombosis. Homozygotes have a 50-100 fold increased risk.
The c.677C>T MTHFR polymorphism is present in the homozygous form in 5-15% of the general population. Individuals who are compound heterozygous or 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 is compound heterozygous for both MTHFR variants. Less is known about the thrombotic risk associated with c.1298 A>C. The c.677C>T variant is also associated with methotrexate toxicity.
The common prothrombin c.20210G>A mutation is associated with elevated prothrombin levels, which promotes development of fibrin clots. 2-4 % of the population is heterozygous for PTV 20210. Heterozygotes have an estimated 3-11 fold increased risk of thrombosis.
Seattle Children’s provides healthcare for the special needs of children regardless of race, color, creed, national origin, religion, sex (gender), sexual orientation 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 or Idaho.
© 1995-2014 Seattle Children’s Hospital, Research and Foundation