[Hemostatic changes in idiopathic venous thrombosis in childhood and adolescence].

The prevalence of inherited thrombotic syndrome in the general population appears to be higher than that of inherited bleeding disorders. The most important candidates for screening are patients with unexplained venous thromboembolism at ages of less than 40 years: In 18 children and adolescents suffering from "idiopathic" vein thrombosis laboratory screening has been performed: PT, PTT, TT, platelet count, spontaneous platelet aggregation, von Willebrand factor, fibrinogen, plasminogen, antithrombin III, protein C, C1-inactivator, alpha-1-antitrypsin, alpha-1-antichymotrypsin, alpha-2-antiplasmin and alpha-2-macroglobulin. Compared to an age matched healthy control group in children with idiopathic vein thrombosis we could demonstrate in vitro platelet activation with significant enhanced platelet aggregation and elevated levels of von Willebrand factor in the onset of the disease. Antithrombin III, protein C, alpha-2-antiplasmin and alpha-2-macroglobulin were significantly decreased. These changes turned to be normal in the following 6 to 9 months. PT, PTT, TT, platelet count, plasminogen, alpha-1-antitrypsin, alpha-1-antichymotrypsin and c1-inactivator showed no alterations compared to the control. Platelet activation and alteration of platelet function in vivo and in vitro is established to initiate thrombosis. The von Willebrand's VIII molecule is involved in this step. The decreased inhibitors of the hemostatic system antithrombin III and protein C in the onset period of thrombotic diseases are discussed to be an increased turnover, whereas the decreased levels of alpha-2-antiplasmin and alpha-2-macroglobulin might be a counter-regulation to the thrombotic event, showing an "activated" fibrinolytic system.