In two studies, we compared the clinical characteristics and outcome of patients with a first episode of VTE and factor V Leiden, prothrombin G20210A, or no thrombophilia.17,18 In 2009, 345 patients had factor V Leiden, 261 had prothrombin G20210A, and 2,399 tested negative. The gene discussed is F2; the disease is Rare hereditary thrombophilia.