Discovered in 1994, in Leiden Netherlands, this mutation is one of the most common genetic risk factors for venous thrombosis (blood clot), and is involved in 20-40% of all cases. Factor V Leiden induces a defect in the natural anti-coagulation system.
Factor five is produced by the liver and circulates in the blood, generally inactive until there is a injury to a vessel wall, than specific proteins will be activated in response to the injury.
Not everyone who gets blood clots will have FVL. There are many reason for any person to be at risk for clots, such as, fractures, hormone replacement therapy, surgery, birth control. Those with FVL can just have a greater risk.