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 was homozygous for factor V Leiden, prothrombin 2021 OA and methylenetetrahydrofolate reductase C677T mutations. All of his relatives who were either triple- or double-heterozygotes were asymptomatic. This observation indicates that thrombophilia is a complex genetic disorder and there is great deal more to be learned about this disease.