Objective: To determine whether resistance to activated protein C caused by the factor V Leiden mutation (Arg506 to Gln) is associated with thrombosis occurring during childhood.
Study design: Children with thrombosis were screened for activated protein C resistance. Children found resistant to activated protein C had DNA analysis for the factor V Leiden mutation. Family members of the children with activated protein C resistance were similarly studied.
Results: Three of fourteen children examined had abnormal normalized activated protein C sensitivity ratios. One child had protein S deficiency. The children had hyperlipidemia. Molecular confirmation of the factor V Leiden mutation was obtained for all three children. Family members of each of the three children were affected.
Conclusions: Children have thromboses in association with the factor V Leiden mutation, as do adults. This mutation may be identified as an isolated risk factor or in association with other risk factors for thrombosis.