A boy with venous thrombosis, homozygous for factor V Leiden, prothrombin G20210A and MTHFR C667T mutations, but belonging to an asymptomatic family

We evaluated a 9-year old boy presenting with deep venous thrombosis who wa s homozygous for factor V Leiden, prothrombin 20210A and methylenetetrahydr ofolate reductase C677T mutations. All of his relatives who were either tri ple- or double-heterozygotes were asymptomatic. This observation indicates that thrombophilia is a complex genetic disorder and there is great deal mo re to be learned about this disease.