Activated protein C resistance

Activated protein C resistance is a hemostatic disorder characterized by a poor anticoagulant response to activated protein C (APC). This results in an increased risk of venous thrombosis, which can cause heart attacks, strokes, and other problems with circulation.

The disorder can be acquired or inherited, the hereditary form having an autosomal dominant inheritance pattern.

Pathophysiology


Activated protein C (with protein S as a cofactor) degrades Factor Va and Factor VIIIa. Activated protein C resistance is the inability of protein C to cleave Factor Va and/or Factor VIIIa, which allows for longer duration of thrombin generation and may lead to a hypercoagulable state. This may be hereditary or acquired. The best known and most common hereditary form is Factor V Leiden. Acquired forms occur in the presence of elevated Factor VIII concentrations.

Associated conditions
Up to 64% of patients with venous thromboembolism might have activated protein C resistance.