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.