R506Q (FV Leiden) mutation in exon 10 of the factor V (FV) gene is highly prevalent in European populations and it has been suggested that the coinheritance of FV Leiden mutation may be an important modifier of hemophilia A phenotype. One other substitution R485K in the same exon, with no functional consequences in vitro, is significantly higher in Thailand and has been associated with thrombophilia. In order to see if any correlation exists between R506Q and hemophilia phenotype and between R485K and thrombosis in Turkish patients, DGGE analysis of exon 10 of the FV gene is carried out among deep venous thrombosis (DVT) and hemophilia A patients. Our results indicate that the allelic frequency of the R485K polymorphism is similar to the frequency detected in Europe, and apparently, is not associated with an increased risk of thrombosis in the Turkish population. It is also not possible to show a modifier effect of FV Leiden on hemophilia A phenotype among the limited number of patients included in this study
