Venous thrombosis is a significant cause of mortality in the U.S., with an annual incidence of 1/1000. It accounts for a half a million hospitalizations and causes over 50,000 deaths annually. Hereditary disorders predisposing to thrombosis include the factor V Leiden genetic mutation, the factor II (prothrombin) gene G to A 20210 mutation, protein C deficiency, protein S deficiency, antithrombin III deficiency, and dysfibrinogenemia.

Of these, the factor V Leiden mutation is by far the most common, accounting for up to 40% of all cases, and up to 75% of cases of recurrent thrombosis. It has approximately a 5% prevalence in the general population and is at least 10 times more common than any other known thrombophilic genetic defect.

In general, thrombophilic patients are targeted. Clinical criteria for thrombophilia includes venous thrombosis or thromboembolism which occurs before the age of 45 or is recurrent, a family history of venous thrombosis or thromboembolism, or a history of thrombosis in an unusual anatomic location, or recurrent superficial thrombophlebitis.

The factor V Leiden mutation can be diagnosed using a simple PCR genetic assay. Unlike conventional coagulation assays, it can be performed in anticoagulated patients.

Genetic counseling is available by calling the Allina Molecular Diagnostics Lab. The Molecular Diagnostic Lab's team of certified genetic counselors will help with any questions about the test or issues for families.

REFERENCES:

1. Dahlback, B Inherited thrombophilia: Resistance to activated protein C as a pathogenic factor of venous thromboembolism. Blood 85:607-614, 1995.
   
   Rosendaal, FR et al. High risk of thrombosis in patients homozygous for factor V Leiden (activated protein C resistance). Blood 85:1504-1508,1995.