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Glucose-6-Phosphate Dehydrogenase (G6PD) Deficiency

• Introduction
• Differential Diagnosis
• Investigation
• Management
• References
• Parent Information handout  (PDF  30KB) 

Introduction

G6PD is a cytoplasmic enzyme in the hexose monophosphate pathway responsible for the production of glutathione. It helps to protect the red blood cell from oxidative damage.

The G6PD gene lies on the X chromosome, and over 300 mutations have been described. Therefore, G6PD deficiency is a common X-linked recessive genetic disorder affecting

• 1 in 50 southeast Asians
• 1 in 10 Mediterranean families (Italian, Greek, and Middle Eastern)
• 1 in 10 African-American.

Because of the high gene frequency in some regions, homozygous affected females are not uncommon. Females may also be affected through Lyonisation or if they have Turner’s Syndrome.

There are 3 major clinical disorders

• neonatal hyperbilirubinaemia
• chronic haemolytic anaemia
• induced haemolytic anaemia
  • naphthalene (mothballs)
  • sulphonamides 
  • nitrofurans 
  • aspirin 
  • fava (broad) beans
  • viral infection

Newborn infants with immature and deficient enzyme pathways are at greater risk of developing haemolytic anaemia than adults. However, neonates usually present with jaundice in the absence of anaemia. Jaundice can be severe and result in kernicterus.

Differential Diagnosis

Causes of haemolytic anaemia

• maternal-fetal blood group incompatibilities
  • rhesus isoimmunisation
  • ABO incompatibility
• other red cell enzyme deficiencies (eg pyruvate kinase)
• red cell membrane disorders (eg hereditary spherocytosis)
• disorders of haemoglobin synthesis (eg alpha thalassaemia group of disorders)

Investigation

• likely findings suggesting further investigation required include
  • unconjugated hyperbilirubinaemia
  • Heinz bodies noted on FBE
  • increased reticulocyte count
  • negative direct anti-globulin titre (Coombs) test
    
    
• diagnostic
  • G6PD screen then assay

Management

• treatment of hyperbilirubinaemia: phototherapy and/or exchange transfusion (may be required at a lower threshold as haemolysing)
• confirmation of diagnosis
• educate parents about G6PD deficiency and avoidance of triggers (especially mothballs)

References

Balnchette V, Doyle J, Schmidt B, Zipursky A. Hematology. In Neonatology: Pathophysiology and Management of the Newborn, 4^th ed. Philadelphia: JB Lipincott Co 1994; 952-999

Web links

RPA Neonatal Unit Protocol: Haemolytic Jaundice   (look under 'Other Causes of Haemolytic Jaundice)

www.aap.org

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