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 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.

Symptoms:

• Pain or tenderness in extremity or affected area
• Redness or swelling in affected area

Note: Symptoms, if present, will be the same as for deep venous thrombosis.

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.

Support Groups:

Expectations (prognosis):

The outcome is usually good with treatment, but recurrences can occur.

Complications:

• Pulmonary embolism
• Recurrent venous clots
• Recurrent pregnancy loss
• Childhood stroke

In rare cases, initial anticoagulation with warfarin can cause transient increased coagulation with severe skin lesions. Patients are at risk if not adequately anticoagulated with heparin prior to taking warfarin.

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.