Published on September 26, 2018
1. Glucose-6-phosphate Dehydrogenase (G6PD) Deficiency (This enzymopathy causes normocytic hemolytic anemia) 9/26/2018 1  G6PD catalyzes the reaction that generates NADPH in the pentose phosphate pathway Glucose-6-phosphate + 2 NADP+ → Ribulose 5-phosphate + CO2 + 2 NADPH  NADPH converts oxidized glutathione (GSSG) to reduced glutathione (GSH) 2 NADPH + GSSG → 2 NADP+ + 2 GSH  GSH protects hemoglobin against oxidative damages (prevents red cell hemolysis) 2 GSH + H2O2 + → 2 H2O + GSSG Abdul-Kader Souid Must know Must know: Glutathione (GSH) is a cytoprotective molecule. It scavenges (detoxifies) reactive oxygen species (ROS), such as hydrogen peroxide (H2O2), superoxide anion (O2 - ), and hydroxyl radical (HO. ). A complete absence of this housekeeping enzyme (G6PD-null mutations) is incompatible with life.
2. G6PD Deficiency 9/26/2018 2  G6PD is an X-linked disorder.  Its prevalence among emirati males is 15% and emirati females 5%.  More than 190 variants (mutations) have been identified. The main one in the Gulf region is the Mediterranean variant.  The Mediterranean variant results from a ‘serine phenylalanine replacement at position 188’ (S188F). G6PD activity declines due to enzyme instability during red cell life span; activity in the reticulocytes is normal.  Clinical manifestations of the Mediterranean variant include being asymptomatic, prolonged neonatal jaundice, and oxidant-induced hemolysis (e.g., fava bean ingestion [favism], Henna, Kohl, and sulfa drugs). • Fava beans contain the potent oxidant divicine (2,6-diamino-4,5-dihydroxypyrimidine).  Treatment of acute hemolysis includes blood transfusion for severe anemia and close monitoring. Avoiding oxidants is essential. Abdul-Kader Souid Must know Divicine
3.  Heterozygous females are susceptible to hemolysis for two reasons: a) Females are genetic mosaics as a result of X-chromosome inactivation (in any cell, randomly only one X chromosome is active). b) In a population in which the frequency of the G6PD-deficient allele is high (such as UAE), homozygous females are not rare. G6PD Deficiency Must know  Acute hemolytic anemia results in dark urine (hemoglobinuria), severe pallor (anemia), Heinz bodies (denatured hemoglobin precipitates), and bite cells. Heinz bodies detected with ‘methyl violet’ staining. Useful to detect during hemolysis, as the enzyme activity would be normal.  Breastfed babies whose mothers have eaten fava beans are also at risk for hemolysis. Prolonged neonatal jaundice may result from Henna (black henna + para-phenylenediamine) or Kohl exposure. Bite cells (arrows) during hemolysis Heinz bodies = oxidized, denatured precipitates of hemoglobin.
4. G6PD deficiency • The diagnosis requires measuring G6PD activity by spectrophotometric analysis of the rate of NADPH production from NADP (normal, 4.5-19.5 units/g hemoglobin). • The level of G6PD activity in reticulocytes (increased during hemolysis) is high, causing false negative results. Thus, G6PD activity is not measured during hemolysis. 9/26/2018 4 Must know Hemoglobin Bilirubin Retic Clinical course (A) and urine analysis (B) of a 13-year-old G6PD-deficient boy during acute infection. Urine is dark in color at the beginning (intravascular hemolysis); as jaundice and hemolysis improve urine becomes progressively clear. Cappellini MD, Fiorelli G. Glucose-6-phosphate dehydrogenase deficiency. Lancet 2008 Jan 5;371(9606):64-74. doi: 10.1016/S0140-6736(08)60073-2. Review. PubMed PMID: 18177777.
5. Case Presentation • A 15-mo-old toddler presents to the ED with a 2-day history of progressive pallor, lethargy, fever and poor feeding. His urine is red-colored. He was seen at a private hospital two days before, and the mother refused blood investigation or admission. • He consumed a large quantity of fava beans two days before, and started to look unwell since then. • His heart rate was 160/min and respiratory rate 60/min. Resuscitation was unsuccessful. 9/26/2018 5 Laboratory Investigation SevereIntravascular Hemolysis Hemoglobin, g/L 37 Ref., 110-140 Reticulocyte count, x109/L 323 Ref., 50-100 Nucleated RBC, x109/L 10 Ref., 0 Total bilirubin, micromol/L 75 Ref., 5-20 Blood film: Red cells with marked polychromasia, many nucleated RBC, fragmented cells (schistocytes) and bite (blister) cells Urinalysis - hemoglobinuria 5+ Ref., negative Respiratory Failure Serum potassium (K+), mmol/L 7 Ref., 3-5 Serum bicarbonate (HCO3 -), mmol/L 4 Ref., 21-30 Arterial pH 6.78 Ref., 7.35-7.45
6. 9/26/2018 6 Case Presentation – 5-year-old boy 1. Severe normocytic anemia 2. Reticulocytosis 3. Indirect (unconjugated) hyperbilirubinemia (hemolysis) 4. Severe G6PD deficiency 5. Blood film: Red cells with polychromasia, nucleated RBC, and bite (blister) cells 6. Urinalysis: 4+ hemoglobin; 0-2 RBC per high-power field. Normal, 5-20 Normal, >4.5 Normal, >11.0 Normal, 35-130 Normal, >75
7. Suggested Reading • Al-Gazali LI, Alwash R, Abdulrazzaq YM. United Arab Emirates: communities and community genetics. Community Genet. 2005;8:186-96. • Abdulrazzaq YM, Micallef R, Qureshi MM, Dawodu A, Ahmed I, Khidr A, Bastaki SMA, Al-Kayat AI, Bayoumi RA: Diversity in expression of glucose-6-phosphate dehydrogenase deficiency in females. Clin Genet 1999;55:13–19. • Bayoumi RA, Nur-E-Kamal MSA, Tadayyon M, Mohamed KKA, Mahboob BH, Qureshi MM, Lakhani MG, Ausiad MO, Kaeda J, Vullamy TJ, Luzzatto L. Molecular characterization of erythrocyte glucose-6-phosphate dehydrogenase deficiency in Al Ain district, United Arab Emirates. Hum Hered 1996; 46:136–141. 9/26/2018 7 Cappellini MD, Fiorelli G. Glucose-6-phosphate dehydrogenase deficiency. Lancet 2008;371:64-74. Kiani F, Schwarzl S, Fischer S, Efferth T (2007) Three-Dimensional Modeling of Glucose-6- phosphate Dehydrogenase-Deficient Variants from German Ancestry. PLoS ONE 2(7): e625. Required Reading
8. Oxidants to be avoided in G6PD deficiency 9/26/2018 8