Reduced protein C activity Protein C deficiency An abnormality of coagulation related to a decreased concentration of vitamin K-dependent protein C. Protein C is activated to protein Ca by thrombin bound to thrombomodulin. Activated protein C degrades factors VIIIa and Va. Protein C can function as an anticoagulant by irreversibly proteolytically inactivating Factor Va and Factor VIIIa. Therefore, a defect in protein C is associated with an increased risk of thrombosis. UMLS:C0398625 SNOMEDCT_US:76407009 HP:0005543 Abnormality of the protein C anticoagulant pathway