What is the distinction between thrombotic thrombocytopenic purpura (TTP) and pediatric hemolytic uremic syndrome (HUS)?

Updated: Nov 12, 2018
  • Author: Robert S Gillespie, MD, MPH; Chief Editor: Craig B Langman, MD  more...
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Hemolytic-uremic syndrome shares many features with thrombotic thrombocytopenic purpura (TTP). For more information, see the Medscape Reference article Thrombotic Thrombocytopenic Purpura. Both diseases include multiorgan dysfunction due to thrombotic microangiopathy, with active hemolysis and thrombocytopenia. The traditional classification describes patients with predominantly renal disease as having hemolytic-uremic syndrome, and patients with predominantly CNS disease as having TTP. However, hemolytic-uremic syndrome can include severe neurologic impairment, and TTP can involve severe renal failure. Involvement of other organ systems also overlaps.

Whether these are, in fact, separate diseases remains controversial; some authors describe "hemolytic-uremic syndrome–TTP" as a single disease entity with a diverse spectrum of presentations. In many cases, both nephrologists and hematologists collaborate on the care of patients with these complex illnesses. Many authors now consider ADAMTS13 activity in distinguishing aHUS from TTP. Patients with very low ADAMTS13 activity, generally less than 10%, are considered to have TTP, while higher levels of activity point to a diagnosis of HUS.

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