Thrombophilia: How To Test? How To Manage?

By Julie Hambleton, MD

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Primary Causes

The primary causes of thrombophilia (Table 2) are genetic in nature and imply an ongoing risk factor for developing VTE that may or may not manifest itself in an individual's lifetime. These genetic variants are independent risk factors for the development of a first episode of "unprovoked" DVT and PE, but their impact on the risk of recurrent disease is less certain for some of the more common mutations. The inherited disorders of thrombophilia pertain to either a quantitative or qualitative abnormality of the natural anticoagulant system. Deficiencies of the natural anticoagulants antithrombin (AT), protein C (PC), and protein S (PS) will be found in only 5% of patients presenting with an unprovoked DVT, although each deficiency on its own is associated with a high relative risk of first episode and recurrent DVT.^1,2 In other words, these are uncommon but potent thrombotic risk factors. In contrast, the factor V Leiden and prothrombin 20210 mutations and hyperhomocysteinemia will be found in 40 to 60% of patients presenting with an unprovoked DVT. However, these defects have a modest impact on the absolute risk of both initial and recurrent DVT.^2,

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