Activated protein C-resistant factor V

Resistance to the anticoagulant effects of activated protein C (APC) (Factor V Leiden heterozygous*) is common: (1,2)

• 5% of the general population
• 25-50% of patients with venous thromboembolism
• 50% of patients with thrombosis who have a family or personal history of thrombosis

APC resistance is usually due to a single point mutation in one or both of the protein C genes. The mutation reduces the susceptibility of factor V to cleavage by APC.

There is increasing evidence that individuals with two or more laboratory characterisable thrombophilic abnormalities (or who are homozygous for either factor V Leiden or prothrombin G20210A) are at a greater risk of thrombosis than those in whom there is a single gene abnormality.

* Factor V Leiden homozygous individuals have an 80x risk of venous thromboembolism

Reference

1. Nakashima MO, Rogers HJ. Hypercoagulable states: an algorithmic approach to laboratory testing and update on monitoring of direct oral anticoagulants. Blood Res. 2014 Jun;49(2):85-94
2. Dahlback B; Advances in understanding pathogenic mechanisms of thrombophilic disorders. Blood. 2008 Jul 1;112(1):19-27.