APRIL 01, 2007
Anna D. Garrett, PharmD, BCPS, CPP

Inherited thrombophilia occurs when an inherited DNA mutation results in the body producing too much or too little of a clotting protein or if the clotting protein does not function correctly. There are a number of hereditary clotting disorders, but the 2 most common are factor V Leiden and prothrombin G20210A mutations.

Factor V Leiden causes factor V protein to be abnormally shaped and prevents it from being broken down by proteins C and S. About 5% of Caucasians carry this mutation, while only 1% to 2% of African Americans, Hispanic Americans, and Native Americans are affected. A prothrombin gene mutation causes the affected individual to produce too much of the prothrombin protein, which increases the tendency to clot. Prothrombin gene mutations occur in 2% to 4% of Caucasians and about 0.4% of African Americans. It is rarer in other groups.

A genetic predisposition to clotting does not mean that the patient will definitely have a blood clot, but knowledge of the problem may be useful for a number of reasons. For example, women who are affected may need to avoid estrogencontaining oral contraceptives and may require use of anticoagulants during pregnancy, since clotting risk increases in pregnancy. Patients who have known thrombophilia should be counseled regarding the signs and symptoms of thromboembolism and be advised to take these symptoms seriously.

Dr. Garrett is a clinical pharmacist practitioner at Cornerstone Health Care in High Point, NC.