In adults, the prognosis of untreated TTP or HUS is extremely poor, with survival rates of only 10%. With plasma exchange, however, survival rates have improved to 80%, although relapses occur in one third of patients with TTP associated with ADAMTS13 autoantibodies. Chronic kidney disease generally does not occur in patients with ADAMTS13 autoantibodies; however, patients may report persistence of minor cognitive symptoms, such as poor concentration or memory.