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Protein S, deficiency
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Prevalence: partial deficiency: 0.12 to 0.21 % of the population, severe deficiency: 1/500,000. Autosomal recessive transmission (sometimes dominant) of a mutation of the PROS1 gene (3q11-q11.2). Protein S is a vitamin K-dependent anticoagulant. It is synthesized in the liver, endothelial cells, megakaryocytes and osteoblasts. It acts as a cofactor of activated protein C. It circulates in the plasma either in its active free form (40 %) or bound to a carrying protein of the complement system (C4bBP for C4b Binding Protein).
Two type are distinguished:
- type I (80 %): where the deficiency is quantitative
- type II: where the deficiency is qualitative (rare). There are subtypes Iia or III (15 %) with a selective deficiency in the free fraction and subtype IIb (< 5 %) which is a functional disorder.
The homozygous form is very rare and presents as a neonatal fulminans purpura. The heterozygous form presents as venous or arterial (or mixed) thrombosis in case of prolonged immobility.
There are acquired forms of protin S deficiency in case of:
- liver failure.
- vitamin K deficiency: dietary deficiency or antivitamine K
- treatment with L-asparaginase or estroprogestational hormones;
- anti-protein S antibody: in case of varicella or disseminated lupus erythematosus
- in some inflammatory syndromes where the increase in C4bBP decreases the free fraction of protein S.
The level of protein S in the term newborn is 12 to 60 %; the adult values are reached between 6 and 12 months of age, but nearly all of the protein S is in the free form up to 3 months of age due to hepatic immaturity (low level of C4bBP).
Anesthetic implications:
antithrombotic prophylaxis with low molecular weight heparin (LMWH).
References :
- Zimmerman AA, Watson RS, Williams JK.
Protein S deficiency presenting as an acute postoperative arterial thrombosis in a four-year-old child.
Anesth Analg 1999; 88: 535-7.
Updated: May 2019