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Updated: Dec 16 2021

G6PD Deficiency

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  • Snapshot
    • A 13-year-old African-American boy presents to his pediatrician for jaundice. He states that he had tried some new Mediterranean food at school today. A day later, he felt fatigued and tired easily after minimal activity and reported back pain. On physical exam, he has scleral icterus. His hemoglobin was found to be 8 g/dL with increased reticulocyte count, increased indirect bilirubin, and decreased haptoglobin. He is given 1 unit of blood.
  • Introduction
    • Clinical definition
      • glucose-6-phosphate dehydrogenase (G6PD) deficiency is an X-linked genetic disorder that causes an intrinsic hemolytic anemia
  • Epidemiology
    • Prevalence
      • 7.1% worldwide
      • most common enzyme disorder of erythrocytes
    • Demographics
      • more severe in males than females
      • common in areas where malaria is endemic
        • sub-Saharan Africa
        • Middle East
        • Southeast Asia
        • Mediterranean regions
        • Pacific islands
    • Genetics
      • inheritance pattern
        • X-linked
      • mutations
        • G6PD gene encoding the G6PD enzyme
  • ETIOLOGY
    • Pathophysiology
      • G6PD affects the pentose phosphate (hexose monophosphate) pathway
        • generates nicotinamide dinucleotide phosphate (NADPH), which protects red blood cells against oxidative stress
        • in red blood cells (without mitochondria), this pathway is the only source of NADPH
        • acute hemolytic anemia following exposure to oxidative stressors
          • primaquine
          • dapsone
          • nitrofurantoin
          • sulfa drugs
          • infections
          • fava bean ingestion
        • oxidative stressors cause
          • rapid depletion of reduced glutathione resulting in
            • precipitation of hemoglobin (manifested as Heinz bodies)
            • erythrocyte membrane damage, both extravascular and intravascular hemolysis
        • G6PD deficiency thought to decrease risk of severe malaria
  • Presentation
    • Symptoms
      • primary symptoms
        • neonatal hyperbilirubinemia on day 2-4
        • acute hemolytic anemia following exposure to precipitants, typically within 24-72 hours after ingestion
          • fatigue
          • jaundice
          • dark urine
          • back pain
    • Physical exam
      • inspection
        • jaundice
          • kernicterus is rare
  • Studies
    • Labs
      • complete blood count and reticulocyte count
      • peripheral smear
        • bite cells (degmacytes)
        • Heinz bodies
      • hemolysis labs
        • ↑ indirect bilirubin
        • ↓ haptoglobin
        • ↑ lactate dehydrogenase
      • urine
        • hemoglobinuria
    • G6PD activity assays
      • indications
        • screening
      • fluorescent spot test
        • most sensitive
      • methemoglobin reduction test
    • Quantitative assays
      • indications
        • confirmation of diagnosis
          • a normal G6PD level immediately after hemolysis does not rule out G6PD deficiency
      • spectrophotometry analysis
      • molecular diagnosis (DNA analysis)
  • Differential
    • Gilbert syndrome
      • jaundice at birth (rather than delayed onset of jaundice)
      • normal G6PD enzyme activity
    • Hereditary spherocytosis
      • spherocytosis seen on peripheral blood smear
        • Disease
        • Peripheral Smear Findings
        • Thalassemia
        • Target cells
        • B12 deficiency
        • Hypersegmented neutrophils
        • Folic acid deficiency
        • Hypersegmented neutrophils
        • G6PD deficiency
        • Heinz bodies and bite cells
        • Asplenia
        • Howell-Jolly bodies
        • Mechanical destruction
        • Schistocytes
        • Microangiopathic hemolytic anemia
        • Schistocytes
        • Hereditary spherocytosis
        • Spherocytes
        • Autoimmune hemolysis
        • Spherocytes
  • Treatment
    • Conservative
      • avoid oxidative stressors
    • Medical
      • blood transfusion
        • indications
          • if hemoglobin < 7 g/dL without hemolysis
          • if hemoglobin < 9 g/dL with hemolysis
      • phototherapy
        • indication
          • neonatal hyperbilirubinemia
  • Complications
    • Recurrence of acute hemolysis
  • Prognosis
    • Natural history of disease
      • typically asymptomatic until exposed to oxidative stressors
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