title: Thrombotic thrombocytopenic purpura and hemolytic uremic syndrome are distinct pathologic entities. A review of 56 autopsy cases.
abstract: BACKGROUND
  Thrombotic thrombocytopenic purpura (TTP) and the hemolytic uremic syndrome (HUS) share many clinical features and have been difficult to separate into distinct entities. Histologic examination of organs from autopsied patients suggested that TTP and HUS have dissimilar lesions of different severity and distribution.
  
  
  OBJECTIVE
  To perform a retrospective observational review of autopsied patients with TTP or HUS to compare the nature and severity of the lesions found.
  
  
  METHODS
  To examine the pathologic features of these conditions, we reviewed all cases among 51 350 indexed autopsies at The Johns Hopkins Hospital (Baltimore, Md) diagnosed with TTP or HUS, and included those showing multiple arteriolar thrombi or their sequela.
  
  
  RESULTS
  The 56 cases that met the inclusion criteria fell into 2 distinct groups, based on distribution and severity of arteriolar lesions. In 25 patients classified as having TTP, platelet-rich thrombi were present-in decreasing severity-in heart, pancreas, kidney, adrenal gland, and brain. In 31 patients with HUS, fibrin/red cell-rich thrombi were present, largely confined to the kidney and often severe, and only 6 cases showed pancreas involvement, 4 adrenal gland involvement, 2 brain involvement, and 1 heart involvement.
  
  
  CONCLUSIONS
  Despite similar clinical features and therapeutic approaches, TTP and HUS each have a characteristic constellation of histopathologic findings. This observation suggests that TTP and HUS are 2 distinct disease entities with different pathophysiologies, and that they do not represent a spectrum of the same disease process.
authors.affiliation: Department of Pathology, The Johns Hopkins Medical Institutions, Baltimore, Md, USA.
authors.forename: Gregory A
authors.initials: GA
authors.lastname: Hosler
authors.forename: Ana M
authors.initials: AM
authors.lastname: Cusumano
authors.forename: Grover M
authors.initials: GM
authors.lastname: Hutchins
mesh_terms: D000293:Adolescent; D000328:Adult; D005260:Female; D006463:Hemolytic-Uremic Syndrome / Q000473:pathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011697:Purpura, Thrombotic Thrombocytopenic / Q000473:pathology*; D012189:Retrospective Studies