Protein C deficiency
Encyclopedia
Protein C deficiency is a rare genetic trait that predisposes to thrombotic disease
Thrombosis
Thrombosis is the formation of a blood clot inside a blood vessel, obstructing the flow of blood through the circulatory system. When a blood vessel is injured, the body uses platelets and fibrin to form a blood clot to prevent blood loss...

. It was first described in 1981. The disease belongs to a group of genetic disorders known as thrombophilia
Thrombophilia
Thrombophilia is an abnormality of blood coagulation that increases the risk of thrombosis . Such abnormalities can be identified in 50% of people who have an episode of thrombosis that was not provoked by other causes...

s. The prevalence of protein C deficiency has been estimated to about 0.2% to 0.5% of the general population. Protein C deficiency is associated with an increased incidence of venous thromboembolism
Thrombosis
Thrombosis is the formation of a blood clot inside a blood vessel, obstructing the flow of blood through the circulatory system. When a blood vessel is injured, the body uses platelets and fibrin to form a blood clot to prevent blood loss...

 (relative risk 8-10), whereas no association with arterial thrombotic disease has been found.

Pathophysiology

The main function of protein C
Protein C
Protein C, also known as autoprothrombin IIA and blood coagulation factor XIV, is a zymogenic protein, the activated form of which plays an important role in regulating blood clotting, inflammation, cell death and maintaining the permeability of blood vessel walls in humans and other animals...

 is its anticoagulant property as an inhibitor of coagulation factors V
Factor V
Factor V is a protein of the coagulation system, rarely referred to as proaccelerin or labile factor. In contrast to most other coagulation factors, it is not enzymatically active but functions as a cofactor...

 and VIII
Factor VIII
Factor VIII is an essential blood clotting factor also known as anti-hemophilic factor . In humans, Factor VIII is encoded by the F8 gene...

. There are two main types of protein C mutations that lead to protein C deficiency:
  • Type I: Quantitative defects of protein C (low production or short protein half life)
  • Type II: Qualitative defects, in which interaction with other molecules is abnormal. Defects in interaction with thrombomodulin
    Thrombomodulin
    Thrombomodulin, CD141 or BDCA-3 is an integral membrane protein expressed on the surface of endothelial cells. In humans, thrombomodulin is encoded by the THBD gene...

    , phospholipids, factors V/VIII and others have been described.


The majority of people with protein C deficiency lack only one of the functioning genes, and are therefore heterozygous. Before 1999, only sixteen cases of homozygous protein C deficiency had been described (two abnormal copies of the gene, leading to absence of functioning protein C in the bloodstream). This may manifest itself as purpura fulminans
Purpura fulminans
Purpura fulminans is a haemorrhagic condition usually associated with sepsis or previous infection. It occurs mainly in babies and small children.It was first described by Guelliot in 1884.- Presentation :...

 in the newborn.

Treatment

Primary prophylaxis with aspirin, heparin or warfarin is often considered in known familial cases. Anticoagulant prophylaxis is given to all who develop a venous clot regardless of underlying cause.

Studies have demonstrated an increased risk of recurrent venous thromboembolic events in patients with protein C deficiency. Therefore, long-term anticoagulation therapy with warfarin
Warfarin
Warfarin is an anticoagulant. It is most likely to be the drug popularly referred to as a "blood thinner," yet this is a misnomer, since it does not affect the thickness or viscosity of blood...

may be considered in these patients.

Homozygous protein C defect constitutes a potentially life-threatening disease, and warrants the use of supplemental protein C concentrates.

Liver transplant may be considered curative for homozygous protein C deficiency.
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