Center for Human Genetics and Laboratory Diagnostics, Dr. Klein, Dr. Rost and Colleagues

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Protein C Deficiency, hereditary [I82.9]

OMIM numbers: 176860612283 (PROC)

Dr. rer. nat. Christoph Marschall

Scientific Background

Protein C is a key enzyme for the regulation of coagulation and the inflammatory response. Activated protein C inactivates, among others, factor Va and VIIIa; thereby coagulation and the formation of thrombin are being inhibited. In addition, protein C exhibits direct and indirect anti-inflammatory activities. Protein C deficiency is inherited in an autosomal dominant manner and is characterized by variable penetrance.

Protein C is encoded by the PROC gene which consists of 9 exons. Heterozygous carriers of PROC mutations with protein C concentrations in the plasma of 25-70% of the norm are symptomatic in 1:16,000 cases of the general population but asymptomatic in 1:500-1:200 cases. Some of the homozygous or combined heterozygous patients with a protein C concentration of less than 25% in the plasma develop purpura fulminans, skin necrosis or disseminated intravascular coagulation at birth; others develop thromboses only during adulthood. Heterozygous carriers are at an increased risk of vein thromboses at a young age.

There are two types of protein C deficiency:

Type I: reduction of concentration and function

Type II: normal or increased concentration and decreased function