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Genetics Home Reference: your guide to understanding genetic conditions     A service of the U.S. National Library of Medicine®

Protein C deficiency

Reviewed May 2013

What is protein C deficiency?

Protein C deficiency is a disorder that increases the risk of developing abnormal blood clots; the condition can be mild or severe.

Individuals with mild protein C deficiency are at risk of a type of blood clot known as a deep vein thrombosis (DVT). These clots occur in the deep veins of the arms or legs, away from the surface of the skin. A DVT can travel through the bloodstream and lodge in the lungs, causing a life-threatening blockage of blood flow known as a pulmonary embolism (PE). While most people with mild protein C deficiency never develop abnormal blood clots, certain factors can add to the risk of their development. These factors include increased age, surgery, inactivity, or pregnancy. Having another inherited disorder of blood clotting in addition to protein C deficiency can also influence the risk of abnormal blood clotting.

In severe cases of protein C deficiency, infants develop a life-threatening blood clotting disorder called purpura fulminans soon after birth. Purpura fulminans is characterized by the formation of blood clots in the small blood vessels throughout the body. These blood clots block normal blood flow and can lead to localized death of body tissue (necrosis). Widespread blood clotting uses up all available blood clotting proteins. As a result, abnormal bleeding occurs in various parts of the body, which can cause large, purple patches on the skin. Individuals who survive the newborn period may experience recurrent episodes of purpura fulminans.

How common is protein C deficiency?

Mild protein C deficiency affects approximately 1 in 500 individuals. Severe protein C deficiency is rare and occurs in an estimated 1 in 4 million newborns.

What genes are related to protein C deficiency?

Protein C deficiency is caused by mutations in the PROC gene. This gene provides instructions for making protein C, which is found in the bloodstream and is important for controlling blood clotting. Protein C blocks the activity of (inactivates) certain proteins that promote blood clotting.

Most of the mutations that cause protein C deficiency change single protein building blocks (amino acids) in protein C, which disrupts its ability to control blood clotting. Individuals with this condition do not have enough functional protein C to inactivate clotting proteins, which results in the increased risk of developing abnormal blood clots. Protein C deficiency can be divided into type I and type II based on how mutations in the PROC gene affect protein C. Type I is caused by PROC gene mutations that result in reduced levels of protein C, while type II is caused by PROC gene mutations that result in the production of an altered protein C with reduced activity. Both types of mutations can be associated with mild or severe protein C deficiency; the severity is determined by the number of PROC gene mutations an individual has.

Related Gene(s)

Changes in this gene are associated with protein C deficiency.

  • PROC

How do people inherit protein C deficiency?

Protein C deficiency is inherited in an autosomal dominant pattern, which means one altered copy of the PROC gene in each cell is sufficient to cause mild protein C deficiency. Individuals who inherit two altered copies of this gene in each cell have severe protein C deficiency.

Where can I find information about diagnosis or management of protein C deficiency?

These resources address the diagnosis or management of protein C deficiency and may include treatment providers.

  • Genetic Testing Registry: Thrombophilia, hereditary, due to protein C deficiency, autosomal dominant (
  • MedlinePlus Encyclopedia: Congenital Protein C or S Deficiency (
  • MedlinePlus Encyclopedia: Necrosis (
  • MedlinePlus Encyclopedia: Protein C (
  • MedlinePlus Encyclopedia: Purpura (
  • National Heart Lung and Blood Institute: How Is Excessive Blood Clotting Treated? (

You might also find information on the diagnosis or management of protein C deficiency in Educational resources and Patient support.

General information about the diagnosis ( and management ( of genetic conditions is available in the Handbook. Read more about genetic testing (, particularly the difference between clinical tests and research tests (

To locate a healthcare provider, see How can I find a genetics professional in my area? ( in the Handbook.

Where can I find additional information about protein C deficiency?

You may find the following resources about protein C deficiency helpful. These materials are written for the general public.

You may also be interested in these resources, which are designed for healthcare professionals and researchers.

What other names do people use for protein C deficiency?

  • hereditary thrombophilia due to protein C deficiency
  • PROC deficiency

For more information about naming genetic conditions, see the Genetics Home Reference Condition Naming Guidelines ( and How are genetic conditions and genes named? ( in the Handbook.

What if I still have specific questions about protein C deficiency?

Ask the Genetic and Rare Diseases Information Center (

What glossary definitions help with understanding protein C deficiency?

acids ; autosomal ; autosomal dominant ; blood clotting ; cell ; clotting ; deficiency ; embolism ; gene ; hereditary ; inherit ; inherited ; necrosis ; protein ; pulmonary ; pulmonary embolism ; purpura ; surgery ; thrombophilia ; thrombosis ; tissue ; veins

You may find definitions for these and many other terms in the Genetics Home Reference Glossary.


  • Brouwer JL, Lijfering WM, Ten Kate MK, Kluin-Nelemans HC, Veeger NJ, van der Meer J. High long-term absolute risk of recurrent venous thromboembolism in patients with hereditary deficiencies of protein S, protein C or antithrombin. Thromb Haemost. 2009 Jan;101(1):93-9. (
  • Cafolla A, D'Andrea G, Baldacci E, Margaglione M, Mazzucconi MG, Foà R. Hereditary protein C deficiency and thrombosis risk: genotype and phenotype relation in a large Italian family. Eur J Haematol. 2012 Apr;88(4):336-9. doi: 10.1111/j.1600-0609.2011.01742.x. Epub 2012 Jan 10. (
  • Goldenberg NA, Manco-Johnson MJ. Protein C deficiency. Haemophilia. 2008 Nov;14(6):1214-21. doi: 10.1111/j.1365-2516.2008.01838.x. (
  • Knoebl PN. Severe congenital protein C deficiency: the use of protein C concentrates (human) as replacement therapy for life-threatening blood-clotting complications. Biologics. 2008 Jun;2(2):285-96. (
  • Mahmoodi BK, Brouwer JL, Ten Kate MK, Lijfering WM, Veeger NJ, Mulder AB, Kluin-Nelemans HC, Van Der Meer J. A prospective cohort study on the absolute risks of venous thromboembolism and predictive value of screening asymptomatic relatives of patients with hereditary deficiencies of protein S, protein C or antithrombin. J Thromb Haemost. 2010 Jun;8(6):1193-200. doi: 10.1111/j.1538-7836.2010.03840.x. Epub 2010 Mar 4. (


The resources on this site should not be used as a substitute for professional medical care or advice. Users seeking information about a personal genetic disease, syndrome, or condition should consult with a qualified healthcare professional. See How can I find a genetics professional in my area? ( in the Handbook.

Reviewed: May 2013
Published: February 1, 2016