Prevalence of the factor V Leiden mutation in children and neonates with thromboembolic disease

Objective: Resistance to activated protein C (APC) has been identified as a risk factor for thrombotic disease in adults. In over 90% of cases, the ba sis for the APC resistance is a mutation in the coagulation factor V gene ( factor V Leiden) that renders the protein more resistant to inactivation by APC. We sought to determine the prevalence of the factor V Leiden (FVL) mu tation in neonates and children who had experienced an arterial or venous t hromboembolic event. Study design: We retrospectively analyzed the clinical records of 33 neonat es and 52 children with thromboembolic disease. Screening for the FVL mutat ion was performed by DNA analysis, allowing for identification of patients as normal, heterozygous, or homozygous. Results: Of the 85 patients studied, 12 (14.1%) were heterozygous for FVL; none were homozygous. Of the 47 patients who had arterial central nervous s ystem events, 8 (17%) were positive for the FVL mutation, including 6 of 22 (27%) neonates. Of those patients who had a venous thrombosis, 4 of 32 (12 .5%) were FVL positive. None of the 85 patients had protein C deficiency, 3 .5% had protein S deficiency, 1.2% had antithrombin III deficiency, and 16. 5% had anti-phospholipid antibodies. Conclusion: These data suggest that the FVL mutation plays a role in the de velopment of arterial and venous thrombotic events in neonates and children .