The Arg506Gln mutation (FV Leiden) among a cohort of 4188 unselected Danish newborns.

Resistance to activated protein C (APC) is the most prevalent single phenomenon associated with thromboembolic disease. It is caused by a single point mutation in the factor V gene (Arg506Gln or FV Leiden), replacing an Arg506 with a Gln at the APC-cleavage site in factor V. In this study we present a prevalence study of the Arg506Gln mutation in a large Danish cohort. By screening 4188 newborns (8376 alleles) we identified 3.4% alleles (95% CI: 3.0-3.8) of the Arg506Gln mutation, corresponding to a heterozygous prevalence of 6.6% (95% CI: 5.9-7.4) in Denmark. This is significantly lower than what has been reported from southern Sweden. The birth cohort has been selected from the entire country, providing representative and accurate estimates of the gene frequencies. Equal gender distribution was found, and the Arg506Gln mutation is probably not a considerable risk factor in fetal life in the general population.