G6PD deficiency

Epidemiology/Background

  • More common in sub-Saharan Africa (malaria protection?)

Pathophysiology

  • G6PD enzyme is responsible for oxidation of G-6-P and reduction of NADP+ to NADPH, which scavenges up free radicals and prevents against associated damage.
    • Only source of NADPH in RBCs- deficiency makes them prone to oxidative damage and haemolysis

Classification

  • Severe (I)- Chronic non-spherocytic haemolytic anaemia;
  • Severe (II)- Less than 10% normal enzyme activity
  • Moderate (III)- 10-60%; Mild (IV)- 60-150%; None (V)- >150%

Presentation

  • Most are asymptomatic.
  • Neonatal jaundice- usually in the neonatal period (may be before, same time or after the time during physiological jaundice occurs)
    • Unconjugated
  • Severe haemolysis can result from triggers (in particular drugs- see below)
    • Beware maternal drugs being passed through breastmilk
  • May have pallor and splenomegaly also

Investigations

  • FBC- anaemia; macrocytosis/reticulocytosis; may show Heinz bodies on blood film
  • Hyperbilirubinaemia
  • Coombs (Direct antibody) test- to exclude ABO/Rhesus incompatibility (most likely negative in G6PD- as these reactions are more likely to occur earlier/more severe)
  • G6PD activity test
  • LFTs

Trigger Drugs

  • Nitrofurantoin and quinolones
  • Sulfonamides (including co-trimoxazole)
  • Dapsone
  • EMLA cream
  • Aspirin
  • Antimalarials
  • Sulfonylureas
  • Vit K analogues

Other triggers include severe infection; DKA; AKI; ‘favism’ due to over ingestion of broad beans (?)

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