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Hereditary thrombophilia / hypercoagulopathies

Protein S deficiency

Reviewer: Jeremy Parsons, M.D. (see Reviewers page)
Revised: 21 June 2012, last major update June 2012
Copyright: (c) 2002-2012, PathologyOutlines.com, Inc.


● Hereditary deficiencies occur in 0.7% of general population
● Many mutations exist (qualitative or quantitative)
● Much lower prevalence of thrombophilia with clustering in families
● Variable penetrance may be due to coexisting risk factors, such as factor V Leiden
● Causes 1-9% of cases of venous thrombosis
● These patients also at risk for warfarin-induced skin necrosis if started on warfarin without the addition of heparin until warfarin levels are therapeutic
● Heterozygotes have levels 35-65% of normal
● First thrombotic event occurs between ages 10-50 years
● 50% risk by age 45
● Homozygotes with severely decreased levels present as newborns with DIC and purpura fulminans, leading to death unless anticoagulation and replacement therapy with fresh frozen plasma is started

Type I (2/3):
● Low free and total protein S antigen, with decreased APC cofactor activity

Type II (rare):
● Normal free and total protein S antigen, and decreased APC cofactor activity

Type III (1/3):
● Normal to low total protein S, low free protein S antigen, and an elevated fraction of protein S bound to C4B protein

Testing recommended:
● Individual with family history who requests testing, to confirm abnormal protein S result
● Must interpret with caution

Testing not recommended:
● During pregnancy or postpartum, during inflammatory, thrombotic or surgical event
● Within 30 days of taking warfarin
● Must delay longer periods for vitamin K antagonists (Phenprocoumon)

Clinical note:
● Acquired protein S deficiency is often seen during pregnancy due to increased C4b, which may reduce levels to 40% or less

Additional references

Arch Pathol Lab Med 2002;126:1349, Haemophilia 2008;14:1222

End of Coagulation > Hereditary thrombophilia / hypercoagulopathies > Protein S deficiency

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