Thrombophilia as a multigenic disorder.

Substantial progress has been made in the study of inherited abnormalities that predispose to venous thrombosis. With new discoveries, the focus has shifted from rare deficiencies associated with high probability for events to relatively common aberrations that produce high risk only in combination. Interactions between inherited and acquired disorders are also attracting much attention. The challenge for the future is how to best discover new risk factors and understand their contributions to multifactorial events.