Congenital protein C or S deficiency is a condition that runs in families (inherited), which is caused by a lack of the proteins C or S in the fluid portion of blood (plasma). Proteins C and S are natural substances that prevent blood clots (anticoagulants). People with this condition are more likely to get blood clots.

Congenital protein C or S deficiency is a disorder that runs in families and causes abnormal blood clotting. Normal blood clotting involves as many as 20 different plasma proteins, called coagulation factors.

A series of complex chemical reactions using these factors takes place quickly to form a protein that doesn't dissolve, called fibrin. This protein stops bleeding by forming a clot. Other plasma proteins, such as proteins C and S, stop or reverse this process to prevent too much clotting.

When certain coagulation factors are low or missing, the chain reaction does not take place normally. This disorder causes an increased risk of clot formation, called thrombosis. Risk factors are a personal or family history of blood clots in the veins.

This disease can be carried via genes in different ways. About 1 out of every 300 people has one normal gene and one faulty gene for protein C deficiency. Protein S deficiency occurs in about 1 in 20,000 people.

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

• Lack of protein C
• Lack of protein S
• Normal thrombin time
• Normal prothrombin time
• Normal partial thromboplastin time
• Normal bleeding time

The drugs heparin and warfarin are used to treat deep venous thrombosis. Patients who have this disorder can take warfarin to prevent another clot.

The outcome is usually good with treatment, but a patient can have symptoms again.

• Pulmonary embolism
• Recurrent clots in the veins
• More than one pregnancy loss
• Childhood stroke

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

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

If your health care 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.

Hoffman R, Benz E, Shattil S, Furie B, Cohen H. Hematology: Basic Principles and Practice. 4th ed. Philadelphia, Pa: Churchill Livingstone; 2004.

Lietz K, Kuehling SE, Parkhurst JB. Hemorrhagic stroke in a child with protein S and factor VII deficiencies. Pediatr Neurol. March 2005;32:208-210.