1. Background

• exposure to a risk factor -> autoimmune phenomenon ->
  -> alters RBC membrane so that membrane now becomes "foreign"
  -> autoantibodies to intrinsic antigens on the RBC surface
  -> formation of immune complexes which attach to RBC surface

  -> hemolysis of RBC's by IgG and/or C3/C4

  -> destruction of RBC's in the reticuloendothelial tissues of the spleen and liver

2. Risk Factors:

1. Anemia

• severe with pallor and/or jaundice
• complications:
  • splenomegaly
  • hemodynamic compromise with shock
  • concomitant ITP (Evans Syndrome)
  • congestive heart failure
  • acute renal failure
  • diarrhea
  • dehydration
• two clinical patterns:

  1. Acute Transient Pattern

  • sudden onset and associated with complications
  • usually in infants or young children
  • usually preceded by an acute infection (i.e., respiratory) or immunization
  • not associated with an underlying systemic illness
  • low mortality with full recovery within 3 months
  • may have frequent exacerbations linked to acute infections

  2. Chronic Pattern

  • insidious onset of signs and symptoms of anemia
  • usually in children > 10 years of age
  • usually associated with an underlying systemic illness
  • 10% mortality rate with hemolysis lasting months to years
  • may be associated with aplastic crises

1. Serum

• Hb: severe, normocytic, normochromic, low or high reticulocytes +/- nucleated RBC's
• smear: spherocytosis, polychromasia
• hemolysis: increased free Hb and unconjugated bilirubin, decreased haptoglobin and hemopexin
• leukocytosis with normal platelets
• positive direct Coombs test:
  • specific
    • for IgG-coated RBC's:
      • antibodies active at 37 C (warm antibodies)
      • specific for certain RBC antigens, i.e,. Rh and LW antigens
      • 80% of chronic cases are IgG specific or mixed
    • "broad-spectrum":
      • for complement-coated RBC's
        • 80% of acute cases are complement specific

2. Bone Marrow

• erythroid hyperplasia also 10% may show decrease in erythroid series

3. Urinalysis

• hematuria, hemaglobinuria

1. Supportive

• hemodynamic compromise:
  • PRBC transfusions (use least incompatible blood)
  • fluid resuscitation
• treat underlying disease
• discontinue offending drug

2. Medications

3. Others - For Chronic Pattern

• splenectomy
• immunosuppressive agents
  • azathioprine, danazol, IV IgG
• plasmaphoresis