Factor V Resistance to Activated Protein C (APC)

By Joel L. Moake, MD, Rice University;Baylor College of Medicine

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Thrombotic Disorders
Overview of Thrombotic Disorders
Antiphospholipid Antibody Syndrome (APS)
Antithrombin Deficiency
Hyperhomocysteinemia
Factor V Resistance to Activated Protein C (APC)
Protein C Deficiency
Protein S Deficiency
Protein Z Deficiency
Prothrombin (Factor II) 20210 Gene Mutation

Mutations of factor V make it resistant to its normal cleavage and inactivation by activated protein C and predispose to venous thrombosis.

Activated protein C (APC), in complex with protein S, degrades coagulation factors Va and VIIIa, thus inhibiting coagulation. Any of several mutations to factor V make it resistant to inactivation by APC, increasing the tendency for thrombosis.

Factor V Leiden is the most common of these mutations. Homozygous mutations increase the risk of thrombosis more than do heterozygous mutations.

Pathways in blood coagulation.

Factor V Leiden as a single gene defect is present in about 5% of European populations, but it rarely occurs in native Asian or African populations. It is present in 20 to 60% of patients with spontaneous venous thrombosis.

Treatment

Anticoagulation

Anticoagulation with parenteral heparin or low molecular weight heparin, followed by oral warfarin, is used for venous thrombosis or for prophylaxis for patients at increased thrombotic risk (eg, by immobilization, severe injury, surgery).

It is not yet known if the newer oral anticoagulants that inhibit either thrombin (dabigatran) or factor Xa (eg, rivaroxaban, apixaban) can be used in place of warfarin for this disorder.

Last full review/revision September 2016 by Joel L. Moake, MD