Factor V Leiden (FVQ 506) is common in a Brazilian population.

Resistance to activated protein C (APC) is the most common risk factor in venous thrombosis. A missense mutation in the factor V gene (factor V Leiden) is the molecular basis for this phenotype. Factor V Leiden was previously found in about 20% of unselected patients with thrombosis but also occurred in 3-5% of healthy Dutch controls. In the present study of Brazilian patients with venous thrombosis we also observed a frequency of 20% for this factor. In addition, in healthy Brazilian controls the frequency of the mutation was 2%. These data suggest that factor V Leiden has a similar distribution worldwide irrespective of the ethnic origin of the population.