Disorders of hemostasis in childhood: risk factors for venous thromboembolism.

In both children and neonates with venous thrombosis, one or more predisposing risk factors can generally be identified. Underlying prothrombotic medical conditions are common in these patients. In addition, a "trigger factor" such as a catheter, surgery or trauma is usually present. However genetic and acquired coagulation abnormalities are also identified in children with venous thrombosis who are appropriately studied. A careful family history and assays for the LA, AT-III, protein C, protein S and the factor V Leiden mutation should be part of the evaluation of infants and children with venous thrombosis.