These inherited disorders of blood coagulation are caused by deficiency of the Vitamin K-dependent plasma proteins C or S that are naturally occurring anticoagulants. The disorder results in an increased tendency for intravascular blood clot formation.
Causes, incidence, and risk factors
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 which are known as blood coagulation factors. A series of complex chemical reactions using these factors takes place very rapidly to form an insoluble protein called fibrin that stops bleeding . Other plasma proteins, such as proteins C and S inhibit or reverse the cascade 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 blood 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 1 out of 20,000 people.
Signs and tests
Deficient protein C
Deficient protein S
Normal thrombin time
Normal prothrombin time
Normal partial thromboplastin time
Normal bleeding time
Treatment
Treatment for deep venous thrombosis includes therapy with heparin and warfarin. Warfarin is usually given preventatively after a first clotting episode in patients identified to have this disorder.
Expectations (prognosis)
The outcome is usually good with treatment, but recurrences can occur.
Calling your health care provider
Call your health care provider if symptoms develop that are suggestive of intravenous clotting (i.e., swelling and redness of the leg).
Prevention
If the disorder is diagnosed, precautions may be taken to avoid thrombus formation in high-risk situations that promote slow movement of the blood in the veins. This occurs with prolonged bed rest usually as a result of an illness, surgery, or hospitalization.