Atypical hemolytic-uremic syndrome

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Background

Pathophysiology

  • Congenital defect leading to dysregulation of the alternative complement pathway, which leads to increased complement activity
  • Mutations can occur anywhere in the complement pathway or, occasionally, in unrelated proteins
    • Complement factor H (CFH), C3, factor B, factor I, CD46
    • Diacylglycerol kinase ε, plasminogen, factor XII (in the presence of anti-factor H autoantibodies), and thrombomodulin (CD141)

Diagnosis

  • Genetic mutation analysis of complement regulatory proteins (CFH, CFI, MCP, C3, CFB, THBD) and anti-CFH antibodies

Management

  • Often unable to distinguish from TTP, so plasma exchange should be initiated promptly
  • If no improvement on PLEX and there is significant renal involvement, consider:
    • Eculizumab to inhibit C5 complement
    • Ideally with full meningococcal vaccination beforehand