Genome.gov | Learning about Factor V Leiden Thrombophilia

What is factor V Leiden thrombophilia?

Factor V Leiden thrombophilia is an inherited disorder of blood clotting. Factor V Leiden is the name of a specific mutation (genetic alteration) that results in thrombophilia, or an increased tendency to form abnormal blood clots in blood vessels. People who have the factor V Leiden mutation are at somewhat higher than average risk for a type of clot that forms in large veins in the legs (deep venous thrombosis, or DVT) or a clot that travels through the bloodstream and lodges in the lungs (pulmonary embolism, or PE).

Factor V Leiden is the most common inherited form of thrombophilia. Between 3 and 8 percent of the Caucasian (white) U.S. and European populations carry one copy of the factor V Leiden mutation, and about 1 in 5,000 people have two copies of the mutation. The mutation is less common in other populations.

A mutation in the factor V gene (F5) increases the risk of developing factor V Leiden thrombophilia. The protein made by F5 called factor V plays a critical role in the formation of blood clots in response to injury. The Factor V protein is involved in a series of chemical reactions that hold blood clots together. A molecule called activated protein C (APC) prevents blood clots from growing too large by inactivating factor V. In people with the factor V Leiden mutation, APC is unable to inactivate factor V normally. As a result, the clotting process continues longer than usual, increasing the chance of developing abnormal blood clots.

Information courtesy of: Genetics Home Reference

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Genome.gov | Learning about Factor V Leiden Thrombophilia