G6PD Deficiency

Aka: G6PD Deficiency, G6PD, Glucose 6 Phosphate Dehydrogenase, Favism, Glucose-6-Phosphate Dehydrogenase Deficiency, Glucose-6-phosphate Dehydrogenase Deficiency Anemia

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II. Epidemiology

  1. Worldwide Prevalence: 400 Million
  2. Caucasians of Mediterranean ancestry (Class II)
    1. Greek patients
    2. Jewish patients
    3. Sardinian patients (from island of Italy)
  3. Black patients or African descent (Class III)
    1. Up to 10% of U.S. african-American Males have G6PD
  4. Asian patients
  5. Filipino patients

III. Pathophysiology

  1. Glucose-6-phosphate dehydrogenase (G6PD)
    1. Catalyzes NADP to NADPH (pentose phosphate path)
    2. Thiol glutathione neutralizes free radicals (superoxide, Hydrogen Peroxide, hydroxyl)
    3. NADPH prevents oxidative damage to cells by regenerating Thiol glutathione after it has been oxidized
    4. RBCs depend on G6PD for sole pathway to NADPH (since RBCs lack mitochondria)
    5. RBCs are most susceptible to insufficient G6PD
  2. Methemoglobin (Fe3+) may form spontaneously
    1. Methemoglobin is typically reduced to normal Hemoglobin (Fe2+) by cellular mechanisms
    2. NADPH is important in combating oxidative stress and converting Hemoglobin back to Fe2+
    3. However in G6PD Deficiency, this fails and Methemoglobinemia is unchecked
  3. Results in acute Hemolytic Anemia
  4. Drug-induced Hemolysis affects older cells
    1. Younger cells have adequate enzyme levels to survive
  5. G6PD mutations occur on distal long arm of C Chromosome
    1. X -Linked Disorder

IV. Grading: Class Severity (WHO)

  1. Abnormal
    1. Class 1: Congenital nonspherocytic Hemolytic Anemia (rare)
      1. Most common in white males of european descent
      2. Hemolysis occurs without oxidative stress exposure
      3. Splenomegaly is present in 40% of patients
    2. Class 2: Severe G6PD (1 to 10% Enzyme Activity)
      1. More common in mediterranean descent
      2. Symptomatic Hemolysis with oxidative stress
    3. Class 3: Mild G6PD (10 to 100% Enzyme Activity, most common)
      1. Hemolytic Anemia occurs only with significant oxidative stress
  2. Normal
    1. Class 4: Nondeficient G6PD Variant (60 to 100% Enzyme Activity)
      1. Common in African Descent
      2. Asymptomatic, even with oxidative stressors
    2. Class 5: Normal activity (>150% normal Enzyme Activity)

V. Causes

  1. See Medications in G6PD Deficiency
    1. Onset within 72 hours of intake
  2. Infection (most common cause)
    1. Salmonella
    2. Eschirichia coli
    3. Beta-hemolytic Streptococcus
    4. Rickettsia
    5. Viral Hepatitis
    6. Influenza A
  3. Fava beans (Italian Broad Beans)
    1. Bell Beans
    2. Broad Beans
    3. English Dwarf Beans
    4. Haba Beans
    5. Horse Beans
    6. Pigeon Beans
    7. Silkworm Beans
    8. Tic Beans

VI. Symptoms and Signs

  1. Usually asymptomatic
  2. See Hemolytic Anemia for acute episodes

VII. Differential Diagnosis

  1. See Drug-Induced Hemolytic Anemia
  2. See Hemolytic Anemia Causes

VIII. Labs

  1. See Hemolytic Anemia
  2. See G6PD Deficiency Detection

IX. Complications

  1. Increased risk of Sepsis

X. Prevention

  1. Avoid precipitating factors
    1. See Medications in G6PD Deficiency
    2. Keep Immunizations up-to-date
  2. Treat Anemia following Hemolytic Anemia episode
    1. Iron Supplementation
    2. Folic Acid supplementation
  3. Measures that are not recommended (no benefit)
    1. Splenectomy
    2. Vitamin E
    3. Selenium

XI. References

  1. Golan in Goldman (2000) Cecil Medicine, p. 873-75
  2. Beutler (1994) Blood 84:3613-36 [PubMed]
  3. Bubp (2015) PT +40(9):572-4 +PMID: 26417175 [PubMed]
  4. Frank (2005) Am Fam Physician 72:1277-82 [PubMed]
  5. Phillips (2018) Am Fam Physician 98(6): 354-61 [PubMed]

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