Hemolytic uremic syndrome.

The thrombotic microangiopathies include both hemolytic uremic syndrome (HUS) and thrombotic thrombocytopenic purpura (TTP). Although debate exists as to whether these are separate entities or a spectrum of disease, both result in the clinical picture of thrombocytopenia, hemolytic anemia, and varying degrees of renal and neurologic involvement. Etiology of HUS includes diarrheal infection due to Shiga toxin-producing bacteria, complement deficiency, pneumococcal infection, and cobalamin deficiency. In disease ascribed to TTP, the main etiologic factor is deficiency of an enzyme known as a disintegrin-like and metalloprotease with thrombospondin type 1 repeats, number 13 (ADAMTS-13). The clinical manifestations may vary, but neurologic involvement can be significant, with reports of hypertensive encephalopathy, seizures, thrombosis and infarct. In nondiarrheal forms of disease, recurrence may occur and clinical diagnosis is essential in order to provide a targeted therapy for the suspected etiology. Therapies include supportive care, cobalamin supplementation, as well as plasma infusion and exchange. End stage renal disease may result and transplantation is curative for some forms of the disease. More recent research focuses on targeted immunotherapy to prevent autoantibody prevention. As of yet, there is no one cure for these potentially devastating diseases, and diagnosis and treatment selection presents a challenge to the clinician.