Atypical hemolytic uremic syndrome (aHUS): essential aspects of an accurate diagnosis

Clin Adv Hematol Oncol. 2016 Nov;14 Suppl 11(11):2-15.

Abstract

Atypical hemolytic uremic syndrome (aHUS), a thrombotic microangiopathy (TMA), is a rare, life-threatening, systemic disease. When unrecognized or inappropriately treated, aHUS has a high degree of morbidity and mortality. aHUS results from chronic, uncontrolled activity of the alternative complement pathway, which activates platelets and damages the endothelium. Two-thirds of aHUS cases are associated with an identifiable complement-activating condition. aHUS is clinically very similar to the other major TMAs: Shiga toxin-producing Escherichia coli (STEC)-HUS, thrombotic thrombocytopenic purpura (TTP), and disseminated intravascular coagulation (DIC). The signs and symptoms of all the TMAs overlap, complicating the differential diagnosis. Clinical identification of a TMA requires documentation of microangiopathic hemolysis accompanied by thrombocytopenia. DIC must be recognized and treated before it is possible to discriminate among the other 3 major TMAs. STEC-HUS can be excluded through testing for Shiga toxin-producing E. coli. aHUS can be distinguished from TTP on the basis of ADAMTS13 (a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13) activity, with a severe decrease characteristic of TTP. This test, as both an activity assay and an inhibitor assay, should be ordered before the initiation of plasma therapy in any patient presenting with a TMA. Finally, it is important to recognize that aHUS remains a clinical diagnosis, but in complex scenarios, tissue biopsy may be a useful adjunct in diagnosis.

Publication types

  • Review

MeSH terms

  • ADAMTS13 Protein / metabolism
  • Algorithms
  • Atypical Hemolytic Uremic Syndrome / blood
  • Atypical Hemolytic Uremic Syndrome / diagnosis*
  • Atypical Hemolytic Uremic Syndrome / etiology
  • Complement Activation
  • Complement System Proteins / genetics
  • Complement System Proteins / immunology
  • Creatinine / blood
  • Diagnosis, Differential
  • Enzyme Activation
  • Humans
  • Platelet Count
  • Purpura, Thrombotic Thrombocytopenic / diagnosis
  • Thrombotic Microangiopathies / diagnosis

Substances

  • Complement System Proteins
  • Creatinine
  • ADAMTS13 Protein