Congenital protein C or S deficiency

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Blood clot formation

Blood clots

These are inherited disorders caused by deficiency of the plasma proteins C or S, which are naturally occurring anticoagulants (they prevent blood clots). Affected people are at increased risk of developing blood clots.

Congenital protein C or S deficiency is an inherited disorder that causes abnormal blood clotting. Normal blood coagulation is a complex process involving as many as 20 different plasma proteins known as coagulation factors.

A series of complex chemical reactions using these factors takes place very rapidly to form an insoluble protein called fibrin, which stops bleeding. Other plasma proteins, such as proteins C and S, inhibit or reverse this process to prevent excessive clotting.

When certain coagulation factors are deficient or missing, the chain reaction does not take place normally. In this disorder, an increased risk of clot formation, called thrombosis, is present. Risk factors are an individual or family history of recurrent blood clots in the veins.

There are different types of genetic transmission of this disease. Heterozygous (one normal gene and one defective) protein C deficiency occurs in approximately 1 in 300 members of the general population. Protein S deficiency occurs in about 1 in 20,000 people.

Review Date: 04/15/2005
Reviewed By: Rita Nanda, MD, Department of Medicine, Section of Hematology/Oncology, University of Chicago Medical Center, Chicago, IL. Review provided by VeriMed Healthcare Network.