Inherited thrombophilia: implications for prevention and treatment of venous thromboembolism.

Inherited thrombophilia, defined as a genetically determined tendency to develop venous thromboembolism (VTE), contributes to the pathogenesis of approximately 40% of VTE episodes. About 50% of carriers of inherited thrombophilic traits develop VTE, but the impact of the different abnormalities is variable in terms of clinical penetrance. Some rare abnormalities (natural anticoagulant deficiencies, homozygous factor V Leiden, and combined defects) result in more severe thrombophilic phenotypes, characterized by early-onset events, more frequent recurrence, and positive family history, whereas the common polymorphisms (heterozygous factor V Leiden and prothrombin G20210A) are associated with lower VTE risk, often in association with triggering risk factors. Therefore, clinical implications of inherited thrombophilia should be assessed in the framework of coexisting and/or circumstantial risk factors involved in the multifactorial pathogenesis of VTE. These considerations should be taken into account when assessing the need and modalities of primary and secondary thromboprophylaxis in patients carrying inherited thrombophilic traits.