Association of the prothrombin G20210A mutation with factor V Leiden in a Midwestern American population

The prothrombin G20210A mutation has been identified as a risk factor for t hrombosis. We studied the relationship between prothrombin G20210A and fact or V Leiden mutations in patients with thrombophilia. The first 264 patient s for whom these molecular diagnostic studies were requested at our institu tion were included in the study. For 116 of the 264 patients, additional co agulation test results were available in the laboratory database. The proth rombin G20210A mutation was found in 16 (6.1%) of the patients ann the fact or V Leiden mutation in 44 (16.7%). Of the 16 patients with the prothrombin G20210A mutation. 8 also carried factor V Leiden: this association was sig nificant. ln contrast, only 2 patients of the 116 with additional coagulati on testing harbored more than I prothrombotic risk factor. These data suppo rt the hypothesis that thrombophilia is a multigenic disorder. Among unsele cted samples from a Midwestern population evaluated for thrombotic risk fac tors, the prevalence of factor V Leiden and prothrombin G20210A mutations a re similar to those found in other populations in the Western world.