Protein C deficiency

Other Names: Autosomal recessive thrombophilia due to congenital protein C deficiency; Autosomal recessive thrombophilia due to PC deficiency; Severe hereditary thrombophilia due to congenital protein C deficiency

Protein C deficiency is a disorder that increases a person's risk to develop abnormal blood clots due to a deficiency of the Protein C, a protein in the body that prevents blood clotting.

Cause

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.

Types

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.

Inheritance

Autosomal dominant pattern, a 50/50 chance.

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.

Signs and symptoms

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.

Diagnosis

A diagnosis of protein C deficiency might be suspected in someone with a deep venous thrombosis (DVT) or a pulmonary embolism, especially if it occurs in a relatively young person (less than 50 years old) or has formed in an unusual location, such as the veins leading to the liver or kidney or the blood vessels of the brain.

Laboratory tests are usually be done to look at the function or quantity of protein C in the blood. Functional tests are usually ordered, along with other tests for abnormal blood clotting, to screen for normal activity of protein C. Based on those results, concentrations of protein C may be measured to look for decreased production due to an acquired or inherited condition and to classify the type of deficiency.

If the shortage of protein C is due to an inherited genetic change, the quantity of protein C available and the degree of activity can be used to help determine whether a person is heterozygous or homozygous for the mutation. Genetic testing is not necessary to make a diagnosis. There are two main types of protein C assays, activity and antigen (immunoassays).Commercially available activity assays are based on chromogenic assays that use activation by snake venom in an activating reagent, or clotting and enzyme-linked immunosorbant assays.Repeated testing for protein C functional activity allows differentiation between transient and congenital deficiency of protein C.

Treatment

Most people with mild protein C deficiency never develop abnormal blood clots and thus do not require treatment. However, people who have experienced a deep venous thrombosis (DVT) or a pulmonary embolism are usually treated with blood-thinning drugs such as heparin or warfarin, which help to prevent another blood clot from developing in the future. Preventative treatment with these blood-thinning drugs may also be considered in those with a family history of blood clotting, as well as in higher risk situations such as pregnancy. A protein C concentrate (Ceprotin®) was approved by the Food and Drug Administration in 2007 for the treatment of protein C deficiency. High doses of intravenous protein C concentrates can help thin the blood and protect from blood clots. However, in those with severe protein C who have had severe bleeding complications on long-term blood thinning therapy, protein C concentrate has been used on a regular basis.

The medication(s) listed below have been approved by the Food and Drug Administration (FDA) as orphan products for treatment of this condition.

• Protein C concentrate (Brand name: Ceprotin) Prevention and treatment of venous thrombosis and purpura fulminans.

Epidemiology

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.

NIH genetic and rare disease info

• NIH info on Protein C deficiency

Protein C deficiency is a rare disease.

Protein C deficiency Resources
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