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Atypical hemolytic uremic syndrome

Definition
aHUS is a complement-mediated disease characterized by microangiopathic hemolytic anemia, thrombocytopenia, and acute renal failure.
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Pathophysiology
aHUS is most commonly caused by dysregulation of the alternative complement pathway.
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Disease course
The failure of complement regulation results in aHUS, which presents with clinical manifestations of microangiopathic hemolytic anemia, thrombocytopenia, and renal failure. Extra-renal manifestations include altered consciousness, seizures, focal neurologic deficits, prodromic diarrhea, hypertension, and malaise. Disease progression may lead to ESRD.
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Prognosis and risk of recurrence
aHUS is associated with an overall mortality rate of 25%.
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Key sources
The following summarized guidelines for the evaluation and management of atypical hemolytic uremic syndrome are prepared by our editorial team based on guidelines from the Korean Working Group on Atypical Hemolytic Uremic Syndrome (KHWG 2016) and the British Society for Haematology (BSH 2010).
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Guidelines

1.Screening and diagnosis

Clinical presentation: suspect aHUS in patients with:
clinical evidence of thrombotic microangiopathy
no evidence of STEC-associated HUS
no evidence of TTP (ADAMTS13 activity > 10%)
B
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2.Diagnostic investigations

ADAMTS13 activity: as per KHWG 2016 guidelines, obtain tests for ADAMTS13 activity to exclude TTP in all patients suspected of having aHUS.
B

More topics in this section

  • Complement testing

  • Shiga toxin test

  • Anti-factor H antibodies

  • Plasma homocysteine, methionine, and MMA

  • Other laboratory tests

  • FACS analysis

  • Genetic testing

3.Diagnostic procedures

Tissue biopsy: consider performing tissue biopsies on a case-by-case basis in patients with suspected aHUS.
C

4.Medical management

Eculizumab
Administer eculizumab, where available, as first-line treatment for patients with symptomatic aHUS.
B
Provide meningococcal vaccination to all patients scheduled to receive eculizumab, prior to administering the first dose.
A

5.Therapeutic procedures

Plasma exchange: as per KHWG 2016 guidelines, offer a trial of plasma exchange and/or plasma infusion to all patients who are clinically suspected of having aHUS, if eculizumab is not available.
B

6.Surgical interventions

Kidney/liver transplantation
Avoid performing renal transplantation alone in patients with aHUS.
D
Consider performing isolated liver transplantation or a combined liver and kidney transplantation in patients with a factor H, factor I, factor B, or C3 mutation.
C

7.Patient education

Trigger avoidance: counsel patients with aHUS who have achieved clinical remission to avoid any identifiable trigger factors as much as possible.
B