Atypical hemolytic-uremic syndrome

Background

• One of the thrombotic microangiopathies
• See also typical hemolytic-uremic syndrome, which occurs after infectious diarrhea

Pathophysiology

• Congenital defect leading to dysregulation of the alternative complement pathway, which leads to increased complement activity

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