Marina Noris

A Putative Role of NO and Oxidant Injury in the Pathogenesis of Hemolytic Uremic Syndrome

Hemolytic uremic syndrome (HUS) is a disease of nonimmune hemolytic anemia, thrombocytopenia, and renal failure due to platelet thrombi in the microcirculation of the kidney. It mainly affects infants and small children, although older children and adults may also suffer. The characteristic lesion, thrombotic microangiopathy (TMA) [1], is unique to this syndrome and consists of vessel wall thickening (capillaries and arterioles), with swelling and detachment of the endothelial cells from the basement membrane and accumulation of fluffy material in the subendothelium (Fig. 21-1). As a result of these changes and occasional thrombi, the glomerular capillary lumina may become occluded. Glomerular thrombi consist of fibrin and platelets, with platelets being preponderant in the early lesions. Extrarenal lesions have also been found, which include microthrombotic lesions in the colon, heart, brain, and pancreas [1]. Typical HUS of children begins with diarrhea, sometimes bloody, and other gastrointestinal symptoms. Classic HUS forms have a remarkably better prognosis than atypical (sporadic or D—) HUS that manifests without prodromal diarrhea in children of all ages and in adults, and accounts for about 5-10% of all cases [2]. The latter usually occurs in families and has a very poor outcome, with end-stage renal failure or death in more than 50% of cases [2].