Activated protein C resistance and the factor V Leiden mutation in children with thrombosis

To determine the prevalence of activated protein C resistance and the factor V Leiden mutation (position 1691, arginine 506 to glutamine substitution) in children with thrombosis, plasma samples from children with thrombosis were tested for activated protein C resistance. DNA was analyzed for the factor V Leiden mutation. Five of 34 children (15%) had activated protein C resistance; each was heterozygous for the factor V Leiden mutation. All 5 children heterozygous for the factor V Leiden mutation suffered non- CNS venous thromboses comprising 21% of the group of children (5/24) with non-CNS venous thrombotic events. Each of these 5 children had a family history of thrombosis. In conclusion, children with non-CNS venous thrombosis should be evaluated for the factor V Leiden mutation. Children most likely affected are those with a family history of thrombosis.