[Activated protein C resistance: role in venous and arterial thrombosis]

Activated protein C resistance is the most prevalent cause of thrombophilia: it is found in 20% to 30% of patients with a history of deep venous thrombosis history. Activated protein C resistance is due to an arginine 506 to glutamine mutation in factor V. This mutation prevents normal inactivation of activated factor V by activated protein C. The estimated increase in relative risk of venous thrombosis is 5 to 10 fold in heterozygotes, and 50- to 100- fold in homozygotes. Activated protein C resistance does not seem to play a role in arterial thrombosis or in the occurrence of myocardial infarction.