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Congenital protein C or S deficiency

Congenital protein C or S deficiency is a lack of proteins C or S in the fluid part of the blood. The proteins are natural substances that help prevent blood clots.


Congenital protein C or S deficiency is an inherited disorder. This means it is passed down through families. Congenital means it is present at birth.

The disorder causes abnormal blood clotting.

1 in 300 people has one normal gene and one faulty gene for protein C deficiency.

Protein S deficiency is much less common and occurs in about 1 in 20,000 people.


If you have this condition, you are more likely to develop blood clots. The symptoms are the same as for deep venous thrombosis, and include:

  • Pain or tenderness in the affected area
  • Redness or swelling in the affected area

Exams and Tests

Laboratory tests will be done to check for proteins C and S.


Blood-thinning drugs are used to treat and prevent blood clots.

Outlook (Prognosis)

The outcome is usually good with treatment, but symptoms may return, especially if blood-thinning agents are stopped.

Possible Complications

Complications may include:

In rare cases, using warfarin to thin the blood and prevent clots can cause brief increased clotting and severe skin wounds. People are at risk if they are not treated with the blood-thinning drug heparin before taking warfarin.

When to Contact a Medical Professional

Call your health care provider if you have symptoms of clotting in a vein (swelling and redness of the leg).


If your provider diagnoses you with this disorder, you should be careful to prevent clots from forming. This can occur when the blood moves slowly in the veins, such as from prolonged bed rest during an illness, surgery, or hospital stay. It may also occur after long airplane or car trips.

Alternative Names

Protein S deficiency; Protein C deficiency


Anderson JA, Weitz JI. Hypercoagulable states. In: Hoffman R, Benz EJ, Silberstin LE, Heslop HE, Weitz JI, eds.Hematology: Basic Principles and Practice

Update Date 11/26/2014

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