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Genetic and Rare Diseases Information Center (GARD)

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Protein C deficiency


* Not a rare disease
Other Names for this Disease
  • Hereditary thrombophilia due to protein C deficiency
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Tests & Diagnosis

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How is protein C deficiency diagnosed?

A diagnosis of protein C deficiency might be suspected in someone with a deep venous thrombosis (DVT) or a pulmonary embolism, especially if it occurs in a relatively young person (less than 50 years old) or has formed in an unusual location, such as the veins leading to the liver or kidney or the blood vessels of the brain.[1]

Laboratory tests are usually be done to look at the function or quantity of protein C in the blood. Functional tests are usually ordered, along with other tests for abnormal blood clotting, to screen for normal activity of protein C. Based on those results, concentrations of protein C may be measured to look for decreased production due to an acquired or inherited condition and to classify the type of deficiency. If the shortage of protein C is due to an inherited genetic change, the quantity of protein C available and the degree of activity can be used to help determine whether a person is heterozygous or homozygous for the mutation. Genetic testing is not necessary to make a diagnosis.[1]
Last updated: 9/20/2011

  1. Protein C and Protein S. Lab Tests Online. March 2011; Accessed 9/20/2011.


  • Orphanet lists international laboratories offering diagnostic testing for this condition. Click here and scroll down the page to learn more about the processes of certification, accreditation, and external quality assessment available to these labs. Click on Orphanet to view the list.