Protein S deficiency

Protein S deficiency
Protein S structure
Specialty	Hematology
Symptoms	Purpura fulminans[1]
Causes	Vitamin K deficiency[1]
Diagnostic method	Coagulation test[1]
Treatment	Heparin, Warfarin[2]

Protein S deficiency is a disorder associated with increased risk of venous thrombosis.^[1] Protein S, a vitamin K-dependent physiological anticoagulant, acts as a nonenzymatic cofactor to activate protein C in the degradation of factor Va and factor VIIIa.^[3]

Decreased (antigen) levels or impaired function of protein S leads to decreased degradation of factor Va and factor VIIIa and an increased propensity to venous thrombosis. Some risk factors for deep vein thrombosis or pulmonary embolism in patients with protein S deficiency include pregnancy, older age, hormonal therapy, consumption of birth control pills, recent surgery, trauma, and physical inactivity.^[4] Protein S circulates in human plasma in two forms: approximately 60 percent is bound to complement component C4b β-chain while the remaining 40 percent is free, only free protein S has activated protein C cofactor activity^{[medical citation needed]}