haemolytic anaemia

see also:

• anaemia

• premature destruction of RBC's resulting in anaemia, haemoglobinuria (if occurs when the amount of free hemoglobin released during hemolysis exceeds available haptoglobin), release of LDH, raised indirect bilirubin and urobilinogen and jaundice (icterus)
• accounts for 5% of all anaemias
• it may be extravascular (ie. RBCs destroyed by spleen or RET such as in hereditary spherocytosis, hypersplenism), or, intravascular (eg. blood transfusion reactions, PNB, prosthetic heart valves)

• G6PD deficiency
  • haemolysis may be triggered by oxidant chemicals (eg. Fava beans, some medications) or stress from infections
• hereditary spherocytosis
• sickle cell disease (SCD)

• autoimmune haemolytic anaemia (AIHA)
  • may occur after allogeneic hematopoietic stem cell transplantation
  • +ve Direct Coomb's test (DAT)
• microangiopathic hemolytic anemia
  • due to:
    • defective prosthetic cardiac valves
    • disseminated intravascular coagulation (DIC)
    • haemolytic uraemic syndrome (HUS)
    • thrombotic thrombocytopenic purpura (TTP)
  • blood film shows fragmented erythrocytes (schistocytes)
• paroxysmal nocturnal haematuria (PNH)
  • due to intravascular complement-mediated destruction of erythrocytes
• immune disorders
• post-transfusion of ABO incompatible blood
• hypersplenism
• toxic chemicals
• medications
• physical damage to RBCs
  • prosthetic heart valves
• infections

• anaemia
• raised serum lactic dehydrogenase (LDH) (also raised in neoplasia or damaged organs)
• decreased serum haptoglobin (Hp) (more likely to occur in mod-severe intravascular haemolysis rather than extravascular)
• raised indirect unconjugated bilirubin (also occurs in Gilbert's disease or cholestasis)
• increased reticulocyte count (may be normal or low if also an aplastic crisis)

• FBE blood film may be helpful
  • presence of thrombocytopenia suggests either:
    • systemic lupus erythematosus (SLE)
    • CLL
    • microangiopathic hemolytic anemias such as thrombotic thrombocytopenic purpura (TTP), haemolytic uraemic syndrome (HUS), prosthetic heart valves
    • Evans syndrome if Direct Coombs also +ve
  • high MCH and MCHC suggests spherocytosis
  • blood film:
    • presence of spherocytes suggests hereditary spherocytosis or AIHA
    • presence of schistocytes suggests microangiopathic hemolytic anemias
  • MCV may be low if iron deficient due to chronic haemolysis
  • MCV may be high if folate deficient due to chronic haemolysis, or if reticulocytosis is present
• consider:
  • USS of spleen to exclude hyperslenism
  • Direct Coomb's test is +ve in > 90% of AIHA and in Evan's syndrome
  • G-6-PD screening
  • cold agglutinin titer, anti-I and anti-I (little i) are elevated in cold agglutinin disease
  • Hb electrophoresis if suspect sickle cell