Medicine & USMLE

Hemolytic Uremic Syndrome (HUS)

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Platelet Disorders
  1. Platelet Plug Formation
  2. Von Willebrand Disease
  3. Bernard-Soulier Syndrome
  4. Glanzmann Thrombasthenia
  5. Immune Thrombocytopenic Purpura (ITP)
  6. Thrombotic Thrombocytopenic Purpura (TTP)
  7. Hemolytic Uremic Syndrome (HUS)
  8. Disseminated Intravascular Coagulation (DIC)

Summary

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Key Points

  • Hemolytic Uremic Syndrome (HUS)
    • Pathogenesis
      • Commonly caused by shiga-like toxin from EHEC (serotype O157:H7) infection
        • Cytokine release damages endothelium → microthrombi formation → consumption of platelets → microthrombi cause mechanical shearing RBCs intravascularly
      • Atypical form (aHUS) is caused by complement gene mutations or autoimmune response
    • Presentation
      • Classically seen in children
        • Most commonly affected by E. coli infections
      • Triad of:
        • Thrombocytopenia
        • Microangiopathic hemolytic anemia (MAHA)
        • Acute kidney injury
      • No fever or neurologic symptoms
        • In contrast to TTP
      • History of bloody diarrhea
        • Associated with EHEC or Shigella
      • Mucocutaneous bleeding
        • Gingival bleeding, menorrhagia, petechiae, epistaxis
    • Diagnosis
      • Decreased platelet count
        • Due to consumptive microthrombi
      • Hemolytic anemia
        • Microthrombi adhesion can shear and damage RBCS
        • Schistocytes seen on peripheral smear
        • Elevated LDH
      • Increased bleeding time
        • Due to decreased platelet count
      • Normal PT/PTT
        • Helps distinguish vs. DIC
    • Treatment
      • Supportive care
        • Fluids to maintain kidney perfusion
        • 3-5% mortality