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Hereditary thrombophilia / hypercoagulopathies

Protein C deficiency

Reviewer: Jeremy Parsons, M.D. (see Reviewers page)
Revised: 20 June 2012, last major update June 2012
Copyright: (c) 2002-2012, PathologyOutlines.com, Inc.


● Hereditary deficiencies occur in 0.14 - 0.5% of general population (the clinically significant incidence is much lower)
● >160 mutations exist, either type I (76%, usually quantitative) or type II (dysfunctional protein, normal protein levels)
● Causes 1-11% of cases of venous thrombosis
● These patients are also at risk for warfarin-induced skin necrosis if treated with warfarin and no heparin until warfarin levels are therapeutic; this paradoxical clotting is due to a faster fall in natural anticoagulant proteins than procoagulant proteins in these patients
● Heterozygotes have levels 35-65% of normal
● First thrombotic event occurs between ages 10-50 years
● Only 30% have thromboembolism, increasing to 75% if coexisting factor V Leiden
● Homozygotes (1 per 500-750K births) with severely decreased levels present as newborns with DIC and purpura fulminans neonatorum, leading to death unless anticoagulation and replacement therapy with fresh frozen plasma is started
● Homozygous protein C deficiency can be cured with liver transplant; however, this is usually too risky so replacement is preferred treatment
● Must exclude acquired causes of protein C deficiency

Acquired causes of low protein C levels

● Clot formation
● Surgery
● Liver disease
● Warfarin (should be discontinued at least 10 days prior to testing) or Vitamin K antagonist therapy
● Vitamin K deficiency
● L-asparaginase therapy

Acquired causes of increased protein C (may mask protein C deficiency)

● Ischemic heart disease
● Pregnancy
● Postmenopausal women
● Hormone replacement therapy
● Oral contraceptives

Clinical images

Warfarin induced skin necrosis

Additional references

Arch Pathol Lab Med 2002;126:1337, Haemophilia 2008;14:1214

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

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