Antiphospholipid antibodies in children

Lupus anticoagulant (LA) is made up of heterogeneous IgG and IgM antibodies that prolong clotting times in vitro and is associated with an increased r ate of both thrombosis and hemorrhage in vivo, although thrombosis is far m ore common. Many mechanisms of action have been explored, but none explains the coagulation abnormality of every sample tested. Binding of these antib odies to protein phospholipid complexes provides a unifying model. Antiphos pholipid antibodies (APAs) are found in adult patients with a variety of di sorders or as an isolated finding. The association of LA and anticardiolipi n antibodies (ACAs) with thrombosis in adults has been established, althoug h there is no test as yet to predict thrombotic risk for an asymptomatic af fected individual. The presentation of thrombosis with postinfectious APA i s uncommon in adults. Children who present with thrombosis and LA are found to have underlying di sorders similar to those of adults. Although the presentation of thrombosis in children with postinfectious LA is rare, the association is established . LA-positive children with thrombosis have manifested a severe acquired de ficiency of protein S; LA-positive children with hemorrhage have manifested an acquired deficiency of prothrombin, The association of thrombosis with ACA-positive children has been reported. Further work to determine the epid emiology, mechanism of action, and thrombotic potential of APA in children is warranted to better understand, prevent, and treat thrombotic and hemorr hagic complications.