Clinical relevance of protein C.

Protein C is, after activation by thrombin, a potent inhibitor of blood coagulation. An isolated deficiency of protein C increases the risk of thrombosis. The two forms of protein C deficiency, the heterozygous and the homozygous deficiency state, have different clinical features. Patients with heterozygous protein C deficiency are at a high risk to develop venous thrombosis and pulmonary embolism. In newborns with homozygous protein C deficiency with very low protein C levels (1%) a purpura fulminans like syndrome was observed. Heparin and coumarin derivatives are effective drugs in heterozygous protein C deficiency, homozygous patients may be treated either by replacement of protein C or coumarin derivatives. Decreased protein C levels were observed in various other diseases: Chronic and acute liver disease, disseminated intravascular coagulation, malignancy, postoperatively and during treatment with asparaginase. The role of protein C in these diseases to trigger thrombosis is not yet established.