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.It may be inherited or acquired. Inherited deficiency of protein C can lead to familial thrombophilia (increased tendency toward thrombosis). It is caused by mutations in the PROCgene, and in most cases is transmitted in an autosomal dominant way; a few people inherit an abnormal allele from both parents and may have a more severe disease (please see autosomal recessive protein C deficiency) because they have very low levels of active protein C. Acquired protein C deficiency may be caused by large blood clots, liver disease, disseminated intravascular coagulation (DIC), infection (sepsis), vitamin K deficiency, use of warfarin or certain types of chemotherapy. While most people with protein C deficiency do not have problems, some are at risk for a type of clot called deep vein thrombosis (DVT), which can travel through the bloodstream and become stuck in the lung, causing pulmonary embolism. Also, abnormal bleeding can occur in various parts of the body causing purple patches on the skin. Treatment depend on the symptoms severity. Most people do not need any treatment. However, in situations of clot risk such as pregnancy, surgery or trauma, prevention treatment may be indicated.
Last updated: 6/7/2017
What causes protein C deficiency?
Protein C deficiency can be inherited or acquired later in life.
Inherited protein C deficiency is caused by mutations in the gene that provides instructions for making protein C, called the PROC gene. These mutations disrupt the protein's ability to control blood clotting. If protein C cannot control blood clotting, abnormal blood clots may form. The mutations are divided into 2 types — type I and type II — on the basis of whether they cause to have lower levels of protein C in the blood (type I) or a functional (type II) deficiency of protein C.
Type I deficiency: When people in the family have only one mutated copy of the gene (heterozygous) they typically have levels that are about one half that of normal patient plasma. Some families have a severe form of the disease and some do not have any symptoms even when they have the same mutation.
Type II deficiency: Type II protein C deficiency is less common than type I disease, and is associated with decreased function of protein C.
When people have two copies of the altered gene (homozygous) or have two different mutations in each copy of the gene (heterozygous) the disease is very severe and protein C deficiency is classically associated with neonatal purpura fulminans (NPF); intracranial thromboembolism may also occur in babies. Some patients present with venous thromboembolism (VTE) in childhood or adolescence.
Protein C deficiency can be hereditary or acquired. Most cases of hereditary protein C deficiency are inherited in an autosomal dominant manner. This means that having only one mutated copy of the responsible gene in each cell (allele) is enough to cause mild protein C deficiency, although some may not have any symptoms. A mutated copy of the gene can be inherited from a person's mother or father.