AbstractIntroduction. In search for explanations of the clinical heterogeneity in patients with haemophilia (PwH) with the same mutation or degree of factor VIII deficiency, the coexistence of single or associated prothrombotic risk mutations has been widely evaluated. Objective. The evaluation of the frequency of prothrombotic risk mutations and polymorphisms in PwH in comparison with the general population. Method. The study was performed on 113 consecutive PwH consisting of PCR technology

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... ing to detect: factor V Leiden - G 1691A (FVL) and prothrombin (PT) - G 20210 A mutations, methylentetrahydrofolat - reductase (MTHFR) and plasminogen activator inhibitor type 1 (PAI-1) polymorphisms. Results. Within the whole study group, 52.21% patients have been identified with associated prothrombotic risk mutations or polymorphisms, 40.70% with one and 7.08% without any such alterations. The global frequency was characterized by the predominance of PAI-1 polymorphism present in 82.29% and MTHFR in 52.21% of patients. Heterozygous variants of PT G20210A, FV G1691A, MTHFR and PAI-1 were found in 7.96%, 9.73%, 39.82% and 53.98% cases, respectively. According to the disease severity, in 89 patients with severe hemophilia, the following frequencies of polymorphisms were found: for MTHFR 52.80%, for FV G1691A 5.61%, for PT G20210A 8.99% and for PAI-1 polymorphism 79.77%. Conclusions. The frequency of FV, PT and PAI-1 genes alterations in our group of hemophilia patients is higher than in the normal population. Nevertheless, considering their uneven distribution in different ethnic groups and geographical regions, more studies on a larger age- and sex-matched patient population are needed.