RESUMEN
Thrombosis among the Thai population is much lower than in western countries. The Thai population is protected to some extent against familial thrombophilia as by the very low prevalence of factor V Leiden, G20210A prothrombin and C677T methylenetetrahydrofolate reductase mutations. The present study reports the prevalence of two mutations of the factor V gene involving the codon for Arg 306 among 500 healthy adult voluntary blood donors (males 285, females 215) and 30 children (boys 20, girls 10) experiencing a total of 36 thrombotic episodes. The blood donors' ages ranged from 18 to 60 years while the children's ages ranged from 9 months to 15 years. The allelic frequencies of the factor V gene mutation of G1091C and A1090G among blood donors were 0% and 0.4%, respectively. Additionally, both mutations were not present in any of the 30 children with thrombosis. The low prevalence of factor V gene mutations in the codon Arg 306 may be relevant to the low rate of thrombosis among the Thai population.