|A service of the U.S. National Library of Medicine®|
Protein C deficiency
On this page:
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.
Read more about the PROC gene.
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.
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?
What if I still have specific questions about protein C deficiency?
Where can I find general information about genetic conditions?
The Handbook provides basic information about genetics in clear language.
These links provide additional genetics resources that may be useful.
What glossary definitions help with understanding protein C deficiency?
acids ; autosomal ; autosomal dominant ; blood clotting ; cell ; clotting ; deficiency ; embolism ; gene ; 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.
See also Understanding Medical Terminology.
References (5 links)
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.