Multicentre evaluation of combined prothrombotic:: defects associated with thrombophilia in childhood

To evaluate the role of multiple established and potential causes of childhood thrombophilia, 285 children with a history of thrombosis aged neonate to 18 years (first thrombotic onset) were investigated and compared with 185 healthy peers. APC-resistance (FV:Q(506)), protein C, protein S, antithrombin, heparin cofactor II (HCII), histidine-rich glycoprotein (HRGP), and prothrombin (F.II), factor XII (F.XII), plasminogen, homocysteine and lipoprotein (a) (Lp(a)) were investigated. In 59% of patients investigated one thrombotic defect was diagnosed, 19.6% showed two thrombotic risk factors, while in 21.4% of children investigated no risk factor could be identified. Single defects comprised established causes of inherited thrombophilia: FV:Q(506) (homozygous n = 10, heterozygous n = 69), protein C (homozygous n = 1; heterozygous n = 31), heterozygous type I deficiency states of protein S (n = 7), antithrombin (n = 7) and homocystinuria (n = 6); potentially inherited clotting abnormalities which may be associated with thrombophilia: F.XII (n = 3), plasminogen (n = 2), HCII (n = 1), increased HRGP (n = 4); new candidate risk factors for thrombophilia: elevated plasma levels of Lp(a) (n = 26), F.II (n = 1). Heterozygous FV:Q(506) was found in combination with heterozygous type I deficiency states of protein C (n = 2), protein S (n = 13), antithrombin (n = 8) and HCII (n = 1), increased Lp(a) (n = 13), and once each with elevated levels of F.II, moderate hyperhomocysteinemia, fibrinogen concentrations > 700 mg/dl and increased HRGP. In addition to the association with FV:Q(506), heterozygous protein C type I deficiency was combined with deficiencies of protein S (n = 2), antithrombin (n = 1), and increased Lp(a) (n = 3). One patient showed protein C deficiency along with familially increased von Willebrand factor > 250%. Besides coexistence with FV:Q(506) and protein C deficiency, protein S deficiency was combined with decreased F.XII and increased Lp(a) in one subject each. Furthermore, we found combinations of antithrombin deficiency/elevated Lp(a), hyperhomocysteinemia/Lp(a), deficiency of HCII/plasminogen, and plasminogen deficiency along with increased Lp(a) each in one. Increased prothrombin levels were associated with fibrinogen concentrations > 700 mg/dl and with HCII deficiency in one child each. Carrier frequencies of single and combined defects were significantly higher in patients compared with the controls. Conclusion In conclusion, data of this multicentre evaluation indicate that paediatric thromboembolism should be viewed as a multifactorial disorder.