Protein c

Definition
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Protein in human blood plasma synthesized in the liver from an inactive precursor, which is vitamin K-dependent. After activation, protein C acts as a serine proteinase. It is a component of the complex regulatory system that is of decisive importance for the physiological process of blood coagulation (haemostasis).

General information
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In principle, several physiological functions are ascribed to protein C:

Anticoagulatory (complex formation with protein S; this activated (APC) complex inactivates the coagulation factors Va and VIIIa by cleaving them)
profibrinolytic
anti-inflammatory (inhibition of the pro-inflammatory cytokines IL-1 and IL-6 (see below interleukins; see below tumour necrosis factor-α).
Apoptosis inhibitor.

Standard value: The standard value is, depending on the method, 70 to 140% in plasma

Clinical picture
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A protein C deficiency can be congenital or acquired:

Congenital protein C deficiency: rare disease. The incidence of a congenital homozygous protein deficit is 1: 160 000 births, in the case of heterozygous deficiency it is 1: 200 in the western world). Symptoms appear already in the first days of life or only in young adulthood.
With acquired protein C deficiency, either production is disrupted (e.g. liver disease) or the consumption of protein C increases excessively (e.g. due to bacterial sepsis). S.a.u. Waterhouse-Friderichsen-Syndrome. Protein C deficiency also plays a decisive role in coumarin necrosis and purpura fulminans.

The clinical picture of congenital protein C deficiency, but also of protein C deficiency acquired e.g. through meningococcal sepsis, first appears in the form of microthrombi on the small skin vessels, but if left untreated it quickly spreads to all other organs. In patients with skin necrosis, purpura fulminans or sepsis, the plasma activity of protein C is drastically reduced. The lower the protein C levels, the more severe the symptoms and the worse the prognosis. Severe symptoms requiring treatment are to be expected with protein C levels of < 20-25% of the protein C standard value.