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