Factor V Leiden thrombophilia Health Article

Definition

Factor V Leiden thrombophilia is a common genetic disorder that leads to a predisposition or increased chance to develop blood clots in the veins (venous thrombosis).

Description

Factor V Leiden thrombophilia is a disorder caused by an inherited change or mutation in the genetic instructions for making a substance called factor V. The factor V change leads to an increased chance to develop blood clots in blood vessels.

Blood clots form in two steps. In the first step, the body produces platelets that are "sticky" and can form initial plugs or clots when needed. However, the first platelets only form the first temporary plugs. To form a more lasting plug or clot the platelets release chemicals to attract more platelets and other substances called clotting factors (or clotting proteins). In the second step, the platelets come together with the clotting proteins and form fibers. The fibers weave together and make the clot stronger and longer lasting.

Individuals affected by factor V Leiden thrombophilia have a genetic mutation that makes a longer lasting, "stickier" form of the clotting factor or protein called factor V. This different form of factor V is called factor V Leiden. The factor V Leiden clotting protein lasts longer in the blood because a chemical produced by the body called Activated Protein C (or APC), which is supposed to help "break-down" the factor V clotting protein, cannot break down the factor V Leiden clotting protein as easily and quickly as it breaks down normal factor V. The factor V Leiden clotting protein breaks down 10 times slower than an average clotting factor V and accordingly stays in the blood longer.

Since there is longer lasting, extra sticky Factor V Leiden in the blood, individuals affected by factor V Leiden thrombophilia have an increased chance to have free-floating blood clots (thrombosis) that can get stuck in the veins and other blood vessels. An alternative name used to describe this condition is Hereditary Resistance to Activated Protein C.