• Decompensated, acquired, immune-mediated haemolytic anaemia
  • Incidence 1 in 100,000
  • Classified serologically:
    • Warm (65%)
    • Cold haemagglutinin disease (29%)
    • Paroxysmal cold haemoglobinuria (1%)
    • Mixed AIHA (5%)
  • 50% of cases are primary, 50% have an underlying cause.
  • Drug-induced AIHA is also recognised, incidence ~1 in 1,000,000
  • Clinical features:
    • Warm AIHA: typically presents with symptomatic anaemia
    • CHAD: may present with acrocyanosis, Raynaud phenomenon or symptoms of anaemia
  • Polyspecific DCT (IgG and C3d) is usually positive in AIHA.
    • Warm AIHA: IgG only (35%), IgG + C3 (56%), C3 only (9%)
    • CHAD: usually C3 only, ~25% also have IgG
    • PCH: C3 only
    • Mixed AIHA: IgG and C3 (requires demonstration of warm and cold antibody with a high thermal amplitude >=30°C)
    • Drug-induced AIHA: IgG, IgG+C3, C3 only or negative
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Blood film features:

  • Spherocytosis
  • Polychromasia with polychromatic macrocytes
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This is the blood film of a patient who had a severe delayed haemolytic transfusion reaction.

Differential diagnosis:

  • DCT Positive (IgG)
    • Primary immune-mediated AIHA
    • Haemolytic transfusion reaction
    • ABO incompatible stem cell transplant
    • Passenger lymphocyte syndrome
    • +/- Drug-induced AIHA
  • DCT Negative
    • Hereditary spherocytosis
    • Paroxysmal nocturnal haemoglobinuria
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The four slides above show blood films and bone marrow aspirates from a patient who had AIHA secondary to B-prolymphocytic leukaemia.

Other features to look for / exclude:

  • Atypical lymphoid cells
  • Thrombocytopaenia (may have associated immune thrombocytopaenia)
  • Agglutination

Causes:

  • Primary immune-mediated warm AIHA
  • Secondary
    • Malignancy (especially chronic lymphocytic leukaemia)
    • Infection (hepatitis C, tuberculosis, HIV etc.)
    • Autoimmune disease
      • Connective tissue disease (especially SLE)
      • Inflammatory bowel disease
    • Post-transplantation

Other Resources: