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Protein S deficiency: causes, symptoms, diagnosis, treatment
Last reviewed: 13.03.2024
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Protein S is a non-enzymatic cofactor of protein C in the inactivation of factors Va and VIIIa, has its own protein-independent C anticoagulant activity.
Protein S, as well as protein C, is dependent on vitamin K and synthesized in the liver. In the circulation it exists in 2 forms - free protein S and associated with the C4-component of complement. Normally 60-70% of protein S is associated with the C4-component of complement - the regulator of the classical pathway of the complement system. The level of binding of protein S to the C4 complement component determines the content of free protein S. Only the free form of protein S serves as a cofactor of activated protein C (APC).
Normally, the protein S level in plasma is 80-120%. In pregnancy, the level of both free and bound protein S is reduced and is 60-80% and lower in the postoperative period.
Protein S deficiency is inherited autosomal dominant. Carriers of gene mutation are more often heterozygous, carriers-homozygotes are rare. It was found that the gene for protein S is located on chromosome 3. Up to 70 mutations of the protein S gene are currently known. The hereditary deficiency of protein S can be of 2 types:
- I type - reduction of the level of free protein S, associated with the C4-component of complement, within the limits of the norm;
- Type II - reduction in the level of free and bound protein S. According to the researchers, the frequency of pregnancy loss is 16.5%. More often observed stillbirths than the early loss of pregnancy.
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Treatment of the protein deficiency S
Treatment of protein deficiency S
Patients with deficiency of protein C and S are refractory to sodium heparin and antiaggregants. However, with acute thrombotic complications, the use of heparin sodium and then low-molecular heparins is justified. As a source of proteins, C and S use fresh frozen plasma in combination with heparin sodium. Out of pregnancy with thrombophilia for a long time used warfarin.