Protein s deficiency

[Oralee]

Because protein S binds and assists activated protein C in the degradation of coagulation factors Va and VIIIa, deficiency of protein S predisposes to venous thrombosis.
(See also Overview of Thrombotic Disorders.)
Protein S, a vitamin K–dependent protein, is a cofactor for activated protein C–mediated cleavage of factors Va and VIIIa. Protein S and protein C are, therefore, components of a natural plasma anticoagulant system.
Heterozygous deficiency of plasma protein S predisposes to venous thrombosis. Heterozygous protein S deficiency is similar to heterozygous protein C deficiency in genetic transmission, prevalence, laboratory testing, treatment, and precautions.
Homozygous deficiency of protein S can cause neonatal purpura fulminans that is clinically indistinguishable from that caused by homozygous deficiency of protein C.
Acquired deficiencies of protein C (and, soon thereafter, protein S) occur during disseminated intravascular coagulation (DIC) and warfarin therapy.
Diagnosis is based on antigenic assays of total or free plasma protein S (free protein S is the form unbound to the protein S carrier molecule, C4-binding protein).