Protein S deficiency
Template:Infobox medical condition (new) Protein S deficiency is a disorder associated with increased risk of venous thrombosis.<ref name="pat">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> 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.<ref>Template:Cite journal</ref>
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.<ref name="clcl">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> 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 activityTemplate:Medical citation needed
Signs and symptoms
Among the possible presentation of protein S deficiency are:<ref name=pat/><ref name=emed/><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref name="clcl"/> Template:Columns-list
Cause
In terms of the cause of protein S deficiency it can be in inherited via autosomal dominance. A mutation in the PROS1 gene triggers the condition. The cytogenetic location of the gene in question is chromosome 3, specifically 3q11.1<ref name="gen">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Protein S deficiency can also be acquired due to vitamin K deficiency, treatment with warfarin, liver disease, kidney disease, chemotherapy, infection, surgery, birth control pills, pregnancy,<ref name="clcl"/> and acute thrombosis (antiphospholipid antibodies may also be a cause as well)<ref name=pat/>
Pathophysiology
In regards to the mechanism of protein S deficiency, Protein S is made in liver cells and the Endothelium.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>Template:Cite journal</ref> Protein S is a cofactor of APC both work to degrade factor V and factor VIII. It has been suggested that Zn2+ might be necessary for Protein S binding to factor Xa.<ref name=emed/><ref name=art/>
Mutations in this condition change amino acids, which in turn disrupts blood clotting. Functional protein S is lacking, which normally turns off clotting proteins, this increases risk of blood clots.<ref name=gen/>
Diagnosis
The diagnosis for deficiency of protein S can be done as part of a thrombophilia investigation, along with reviewing family history of thrombotic disease.<ref name=pat/><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Testing for protein S deficiency should be delayed if there are causes for acquired deficiency or interfering factors.<ref name = "ISTH">Marlar RA, Gausman JN, Tsuda H, Rollins-Raval MA, Brinkman HJM. Recommendations for clinical laboratory testing for protein S deficiency: Communication from the SSC committee plasma coagulation inhibitors of the ISTH. J Thromb Haemost. 2021 Jan;19(1):68-74. doi: 10.1111/jth.15109. PMID 33405382.</ref>
The initial assay for congenital protein S deficiency should be the free protein S antigen assay. If the level is low, total protein S antigen assay can be performed to differentiate between type I and type III deficiency. Protein S activity assays may be useful in patients with a normal free protein S antigen in occasional situations: 1) if no abnormality is identified during a thrombophilia workup, but clinical suspicion persists; or 2) in specific populations in which type II deficiencies are more common.<ref name="ISTH" />
Screening with a free protein S antigen assay is preferred because there are fewer interferences compared to assays for protein S activity, as well as better assay performance characteristics.<ref name="ISTH" />
Differential diagnosis
Other causes for thrombophilia are- Antiphospholipid syndrome, Factor V Leiden and Prothrombin G20210A mutations, protein C deficiency and antithrombin deficiency (though this list is not exhaustive)<ref name=emed/>
Types
There are three types of hereditary protein S deficiency:<ref name="emed">Template:Cite journal</ref><ref name=gen/>
- Type I – decreased protein S activity: decreased total protein S levels, as well as decreased free protein S levels
- Type II – decreased in regards to the cofactor activity of the protein
- Type III – decreased protein S activity: decreased free protein S levels (normal total protein S levels)
Treatment
In terms of treatment for protein S deficiency the following are consistent with the management (and administration of) individuals with this condition (the prognosis for inherited homozygotes is usually in line with a higher incidence of thrombosis for the affected individual<ref name=pat/>):<ref name=emed/><ref name="art">Template:Cite journal</ref>
- Unfractionated heparin (w/ warfarin)
- LMWH/Low molecular weight heparin
- Dabigatran
- Direct Factor Xa Inhibitors
- Graduated compressed stocking
- High degree of prophylaxis
References
Further reading
External links
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