Group 6

• G6PD deficiency


  A hereditary condition caused by a structural defect in the G6PD enzyme
• G6PD enzyme


  • Crucial "housekeeping" enzyme vital for red blood cell survival and their response to oxidative stress
  • Most common enzyme deficiency globally, impacting approximately 400 million individuals, especially those of African, Asian, and Mediterranean descent
• Inheritance pattern


  1. linked recessive, predominantly affecting males
• G6PD deficiency exhibits polymorphism, with over 300 variants identified
• The disorder offers partial protection against malaria, and its prevalence corresponds to historical malaria distribution, explaining the persistence and high frequency of associated genes
• Clinical manifestations of G6PD deficiency

  • Neonatal jaundice
  • Episodes of intravascular hemolysis and consequent anemia triggered by infections, medications inducing oxidative stress, ingestion of fava beans, ketoacidosis
  • Chronic hemolytic anemia
• Hemolysis in G6PD deficiency

  Typically starts 24 to 72 hours after exposure to oxidative stressors, and can present with weakness, tachycardia, jaundice, hematuria
• Management of G6PD deficiency

  1. Avoiding triggers like fava beans, certain drugs, and chemicals causing oxidant stress

  2. Identifying and discontinuing the precipitating agent for managing hemolysis

  3. Acute hemolysis typically resolves in 8 to 14 days and rarely requires transfusion for severe anemia

  4. Infants with prolonged neonatal jaundice benefit from phototherapy, and exchange transfusion may be necessary in severe cases

  5. Individuals with chronic hemolysis or nonspherocytic anemia should take daily folic acid supplements

  6. Long-term follow-up with a hematologist is recommended for comprehensive management and monitoring
• G6PD gene


  Located on the distal long arm of the X chromosome at Xq28 locus, 18 kilobases (kb) long with 13 exons, encoding a 515 amino acid G6PD enzyme, with 186 documented mutations, mostly single-base changes causing amino acid substitutions
• G6PD deficiency variants


  • G6PD A+ variant: High enzyme levels, no hemolysis
  • G6PD A- variant: Lower enzyme levels, acute intermittent hemolysis, common in African, Mediterranean, and Asian populations
  • G6PD Mediterranean (Mediterranean G6PD A-): More severe enzyme deficiencies, fava bean hemolysis common
  • G6PD B: Wild type allele, normal variant
• WHO classification of G6PD variants

  • Class I: Most severe deficiencies
  • Class II: G6PD Mediterranean deficiency (typically less severe than Class I)
  • Class III: G6PD A- deficiency, moderate enzyme deficiency
  • Classes IV and V: No clinical significance in enzyme deficiency or hemolysis severity
• G6PD enzyme function


  Catalyzes oxidation of glucose-6-phosphate and reduction of NADP+ to NADPH, which maintains reduced glutathione, acting as an oxidative metabolite scavenger
• Red blood cells


  • Depend solely on G6PD activity for NADPH production, crucial for protection against oxidative stresses
  • Highly susceptible to oxidative stresses due to their reliance on G6PD for NADPH generation
• G6PD deficiency


  Oxidative stresses can denature hemoglobin, leading to intravascular hemolysis
• Heinz bodies


  Denatured hemoglobin visible in peripheral blood smears with supravital staining
• Degree of G6PD deficiency

  Minimally reduced enzyme levels do not cause hemolysis, greater deficiency leads to hemolysis triggered by infections, certain drugs, fava beans, or ketoacidosis, severe deficiency results in chronic hemolysis, often presenting as non-spherocytic hemolytic anemia
• Neonatal jaundice in G6PD-deficient infants


  Due to imbalance between bilirubin production and conjugation, inefficient bilirubin conjugation contributes to jaundice, especially in borderline premature infants
• Most patients with G6PD deficiency are asymptomatic
• Acute hemolysis in G6PD deficiency

  Self-limiting, resolving within 8 to 14 days, targeting aging RBCs with low G6PD levels, new RBCs produced to compensate for anemia have high G6PD levels, making them resistant to oxidative damage and limiting hemolysis duration
• Jaundice and splenomegaly may be present in severe hemolysis cases, right upper quadrant tenderness due to hyperbilirubinemia and cholelithiasis may occur, skin ulcers, though infrequent, can be a complication in severe G6PD deficiency cases
• Indications for testing for G6PD deficiency

  • Development of hemolysis after exposure to medications or conditions inducing oxidant stress
  • Unexplained or prolonged neonatal hyperbilirubinemia
  • Non-spherocytic hemolytic anemia, as severe G6PD deficiency can be the underlying cause
• Tests to diagnose hemolysis

  • Complete blood cell count (CBC) and reticulocyte count
  • Lactate dehydrogenase (LDH) level
  • Indirect and direct bilirubin level
  • Serum haptoglobin level
  • Urinalysis for hematuria
  • Urinary hemosiderin
  • Peripheral blood smear
• Tests to diagnose G6PD deficiency

  • Screening for G6PD deficiency in patients with a suggestive family history or in geographical areas with a high prevalence
  • Positive screening results should be confirmed by quantitative tests
  • Molecular analysis of G6PD useful for population screening, family studies, females, and prenatal diagnosis
  • Beutler test (semi-quantitative rapid fluorescent spot test)
  • Quantitative assay of G6PD activity (spectrophotometric analysis)
• Diagnosis challenges in females

  Females may be hemizygous, have skewed X chromosome inactivation, or exhibit G6PD gene mosaicism, complicating G6PD diagnosis
• Timing of G6PD deficiency testing

  Perform testing when patients are in remission, as acute hemolysis can yield falsely negative results due to destroyed older erythrocytes with diminished G6PD levels
• Spectrophotometric analysis limitations: Older erythrocytes are destroyed during hemolysis due to diminished G6PD levels, making them vulnerable, and compensatory increase in immature erythrocytes and reticulocytes with higher G6PD levels can skew results during acute hemolysis
• Beutler test


  Semi-quantitative rapid fluorescent spot test that detects NADPH generation from NADP. Positive result if blood spot fails to fluoresce under UV light. Not reliable for diagnosing G6PD deficiency in females.
• Quantitative assay of G6PD activity

  Spectrophotometric analysis of G6PD activity in a leukocyte-depleted sample
• Testing for G6PD deficiency

  1. Perform testing when patients are in remission

  2. Acute hemolysis can yield falsely negative results due to destroyed older erythrocytes with diminished G6PD levels
• Spectrophotometric analysis limitations


  • May fail to detect G6PD deficiency in hemizygous patients
  • May also fail to detect deficiency in heterozygous females due to residual activity in G6PD-sufficient cells
• Alternative methods for sensitive testing in females

  • Cytochemical method or cytofluorometry: Identifies G6PD-deficient and G6PD-sufficient cells, enhancing sensitivity
  • Chromate inhibition test: More sensitive than spectrophotometric quantitation for heterozygous G6PD deficiency in females
• Rapid point-of-care diagnostic tests for G6PD deficiency


  Developed for quick determination of G6PD deficiency status. Potential role in malaria-endemic areas to ensure safe use of primaquine.
• Newer versions of rapid tests

  Quantitative and suitable for use in males, females, and neonates
• G6PD activity in infants

  Higher in premature infants compared to term infants. Important to consider when testing for G6PD deficiency in this population.
• Most individuals with G6PD deficiency do not require treatment
• Education for patients with G6PD deficiency

  • Avoid drugs and chemicals inducing oxidant stress
  • Avoid consumption of broad beans (fava beans)
• Favism


  A complication of G6PD deficiency, primarily associated with the Mediterranean variant
• Managing hemolysis in G6PD deficiency

  1. Identification and discontinuation of the precipitating agent

  2. Treat anemia appropriately, considering that hemolysis is self-limited and typically resolves within 8 to 14 days
• Transfusions are rarely necessary in G6PD deficiency-related hemolysis
• Splenectomy is generally ineffective in managing G6PD deficiency-related hemolysis