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Protein S deficiency

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Title: Protein S deficiency  
Author: World Heritage Encyclopedia
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Subject: List of MeSH codes (C15), Hematologic disease, Sticky platelet syndrome, Venous thrombosis, Nutritional anemia
Collection: Coagulopathies
Publisher: World Heritage Encyclopedia

Protein S deficiency

Protein S deficiency
Classification and external resources
ICD-10 D68.5
ICD-9-CM 289.81
OMIM 176880
DiseasesDB 10814
eMedicine med/1924
MeSH D018455

Protein S deficiency is a disorder associated with increased risk of venous thrombosis. Protein S, a vitamin K-dependent physiological anticoagulant, acts as a nonenzymatic cofactor to activate protein C in the proteolytic degradation of factor Va and factor VIIIa. Decreased (antigen) levels or impaired function (activity) of protein S leads to decreased degradation of factor Va and factor VIIIa and an increased propensity to venous thrombosis. 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.


There are three types of hereditary protein S deficiency:

  • Type I - decreased protein S activity: decreased total protein S (=both bound and free protein S) levels AND decreased free protein S levels (quantitative defect)
  • Type II - decreased protein S activity: normal free protein S levels AND normal total protein S levels (qualitative defect)
  • Type III - decreased protein S activity: decreased free protein S levels AND normal total protein S levels (quantitative defect)

Protein S deficiency can also be acquired due to vitamin K deficiency or treatment with warfarin, systemic sex hormone therapy and pregnancy, liver disease, and certain chronic infections (for example HIV). Vitamin K deficiency or treatment with warfarin generally also impairs the coagulation system itself (factors II, VII, IX and X), and therefore predisposes to bleeding rather than thrombosis. Protein S deficiency is the underlying cause of a small proportion of cases of disseminated intravascular coagulation (DIC), deep venous thrombosis (DVT) and pulmonary embolism (PE).

External links

  • Protein S Deficiency And Thrombophilia at
  • Protein S Deficiency—University of Illinois


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