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Although symptomatic thrombotic disease in children is rare when compared to adults, it is an increasing concern since, as care of children with chronic, previously life-threatening medical conditions improves, the incidence of thrombosis in children increases. It is important for providers to understand the prevention, diagnosis, and treatment of thrombosis as its occurrence can lead to mortality or life-long sequelae.
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The overall incidence of thrombosis formation in children is not precisely known, as there are few prospective studies. The reported rate in hospitalized patients is 5.3 per 10,000, with a bimodal peak in the neonatal and adolescent age groups. It is not clear whether the marked increase in thromboses that have been reported over the past decade represents a true increase in the frequency or simply a result of improved recognition and detection in children.
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Thrombosis has 3 main causes: reduced blood flow (stasis), increase in blood coagulation factors (hypercoagulability), and abnormalities in the vessel wall, otherwise known as Virchow’s triad. Once the endothelium is injured, platelet adhesion is accompanied by platelet aggregation and thrombin formation. This process is usually tightly regulated in order to prevent excessive bleeding or clotting. However, at times, the process is uncontrolled, and a thrombus can form in excessive amounts or in an unusual place, causing harm.
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Thrombosis during childhood is a multifactorial event caused by both genetic and acquired risk factors. Most children with thrombosis have an underlying medical condition that alters the hemostatic system to induce activation of coagulation and/or to prevent the inhibition of coagulation. The majority of conditions are related to inflammation or to abnormal blood flow (Table 434-1). Many children also have the additional risk factor of having a central venous catheter (CVC) that was inserted to facilitate therapy for their underlying illness. The use of CVCs constitutes the most common acquired risk factor for thrombosis. More than half of children with thrombosis will also have an inherited prothrombotic abnormality (Table 434-2), but the clinical relevance of congenital thrombophilia in asymptomatic children or in the presence of an acquired risk factor (eg, the presence of a CVC) in childhood is still uncertain.
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