Risk factors for venous thrombosis in Swedish children and adolescents

Aim: To identify prothrombotic risk profiles in children and adolescents referred to a regional coagulation centre in southern Sweden for a first thrombotic event. Methods: One hundred and twenty-eight consecutive children and adolescents ( newborn to 20 y) referred for evaluations of a first episode of venous thrombosis were investigated. Clinical data were collected retrospectively, and the following variables were investigated: protein C, protein S, antithrombin; resistance to activated protein C; the genotypes FV-G1691A, F II-G20210A, MTHFR-C677T, MTHFR-A1298C; coagulation factors VIII and XI. Results: 104/128 subjects (81%) had identifiable acquired risk factors, most often indwelling catheters and hormone therapy. Predisposing genetic factors related to thromboembolic events were revealed in 53/83 (64%) of subjects who agreed to follow-up blood sampling, and 17/83 (20%) had two or more inherited risk factors. Combinations of genetic and acquired risk factors were identified in 45/83 (54%) of the subjects, and 77/83 (93%) had at least one such risk factor. Both sexes had one peak in frequency at less than 1 y of age and then an increase during adolescence, more in females than in males. Plasma values for coagulation factors VIII and XI were age appropriate and showed a normal Gaussian distribution. Conclusion: This study identified prothrombotic risk profiles in almost all children and adolescents with venous thrombosis, which underlines the importance of careful evaluation of genetic and acquired risk factors.