Protein C deficiency

Protein C deficiency is a rare genetic trait that predisposes to thrombotic disease. It was first described in 1981. The disease belongs to a group of genetic disorders known as thrombophilias. 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 (relative risk 8-10), whereas no association with arterial thrombotic disease has been found.

Pathophysiology
The main function of protein C is its anticoagulant property as an inhibitor of coagulation factors V and VIII. 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, 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 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 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.