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.
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.
The outcome is usually good with treatment, but symptoms may return, especially if blood-thinning agents are stopped.
Complications may include:
- Childhood stroke
- More than one pregnancy loss (recurrent miscarriage)
- Recurrent clots in the veins
- Pulmonary embolism
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.
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. 6th ed. Philadelphia, PA: Elsevier; 2013:chap 142.
Review Date 11/26/2014
Updated by: Yi-Bin Chen, MD, Leukemia/Bone Marrow Transplant Program, Massachusetts General Hospital, Boston, MA. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.