Hemolytic uremic syndrome (HUS) is a rare disease of microangiopathic hemolytic anemia, thrombocytopenia, and renal impairment. Typical HUS follows a diarrheal illness caused by a verocytotoxin-producing bacterium, commonly Escherichia coli O157:H7, and resolves in most cases without sequelae. 1 Atypical HUS (aHUS) is much less common and has a considerably worse prognosis in terms of both mortality and development of ESRD. 2 Mutations in genes encoding complement regulatory proteins and

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... ry disorders of complement regulation seem to play a central role in the pathogenesis of most cases of aHUS. Triggering of an unregulated complement cascade is thought to damage endothelium, producing microangiopathic hemolytic anemia and thrombosis. Gene mutations