Impaired fibrinolysis in the hemolytic-uremic syndrome of childhood.

Thrombotic obstruction of glomerular capillaries causes acute renal failure in patients with hemolytic-uremic syndrome (HUS). Recanalization of occluded vessels normally occurs by activation of the endogenous fibrinolytic system, mediated by plasminogen activators, which are stored and synthesized in the endothelial cells. However, endothelial injury is considered the primary event in the pathogenesis of HUS, and this may result in impaired fibrinolysis. In five children with HUS we performed a prospective study of plasminogen activator activity and two plasminogen activator antigens: tissue-type plasminogen activator and urokinase-type plasminogen activator before and after intravenous desmopressin. Plasminogen activator inhibitor type-1 antigen was also studied. In the acute stage of HUS plasminogen activating activity was low, in spite of elevated levels of total plasminogen activator antigens. This decrease of plasminogen activating activity was due to high levels of the plasminogen activator inhibitor. Improvement of fibrinolysis paralleled recovery from HUS. We conclude that decreased fibrinolysis is an important pathophysiologic feature of HUS.