Ulcerative Colitis and Atypical Hemolytic-Uremic Syndrome: An Unusual But Potentially Life-threatening Complication

Abstract Hemolytic-uremic syndrome (HUS) is defined as the triad of nonimmune hemolytic anemia, thrombocytopenia, and acute renal failure, in which the underlying lesions are mediated by systemic thrombotic microangiopathy (TMA). The atypical HUS (aHUS) can be considered a subtype of HUS that is rare in childhood and has a worse prognosis. Recent findings have established that the TMA in aHUS are consequences of the disregulation of the complement activation, leading to endotelial damage mediated by the complement terminal pathway.1, 2 Likewise, previous research suggests an important role for the deregulation of the alternative complement cascade in the pathogenesis of inflammatory bowel disease (IBD).3, 4 We report the case of a patient with ulcerative colitis (UC) who developed aHUS during a flare-up of her chronic disease. This association is extremely infrequent and had been previously reported in only 1 patient.5