Protein C in thromboembolic disease.

Human protein C is the central protein of an important regulatory mechanism, as shown by the high incidence of thromboembolic complications in congenital deficiencies of protein C. Both abnormal molecules and half-normal levels of protein C antigen and activity have been found in patients with familial thrombotic complications. Newborn infants with congenital homozygous protein C deficiency develop catastrophic thrombosis (purpura fulminans) and will not survive beyond the neonatal period without protein C replacement. Individuals with systemic thrombosis have significantly decreased levels of protein C concomitant with the severity of the DIC. These studies suggest that protein C is important not only in the congenital deficiencies, but also in acquired deficiencies, such as during DIC or possibly the postsurgical hypercoagulable state.