Glucose-6-phosphate dehydrogenase deficiency
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-In-Chief: Priyamvada Singh, M.D. [2]
Overview
Historical Perspective
Classification
Pathophysiology
Causes
Differentiating Glucose-6-phosphate dehydrogenase deficiency from other Diseases
Epidemiology and Demographics
Risk Factors
Screening
Natural History, Complications and Prognosis
Diagnosis
History and Symptoms | Physical Examination | Laboratory Findings | Electrocardiogram | Chest X Ray | CT | MRI | Echocardiography or Ultrasound | Other Imaging Findings | Other Diagnostic Studies
Treatment
Medical Therapy | Surgery | Primary Prevention | Secondary Prevention | Cost-Effectiveness of Therapy | Future or Investigational Therapies
Case Studies
History and Symptoms
History
- Patients are almost exclusively male, due to the X-linked pattern of inheritance, but female carriers can be clinically affected due to lyonization where random inactivation of an X-chromosome in certain cells creates a population of G6PD deficient red cells coexisting with normal red cells.
- History of hemolytic crises occurs 2-4 days in response to:
- Certain drugs:
- Primaquine (an antimalarial)
- Sulphonamide antibiotics
- Sulphones (e.g. dapsone, used against leprosy)
- Other sulphur-containing drugs: glibenclamide (an anti-diabetic drug)
- Nitrofurantoin (an antibiotic often used for urinary tract infections)
- Vitamin K analogues
- Several others[1]
- Henna can cause a haemolytic crisis in G6PD deficient infants.[2]
- Certain foods, most notably broad beans
- Illness (severe infections)
- Diabetic ketoacidosis
- Certain drugs:
Symptoms
- Symptoms suggestive of anemia such as fatigue, palpitation
- Prolonged jaundice
- Hemolytic features like dark colored urine
- Abdominal or back pain
- Very severe crises can cause acute renal failure
Diagnosis
Laboratory diagnosis
The diagnosis is generally suspected when patients from certain ethnic groups develop anemia, jaundice and symptoms of hemolysis after challenge to any of the above causes, especially when there is a positive family history. The hemolysis spontaneously resolves in approximately 1 week as the older enzyme-depleted cells are replaced by new cells with sufficient G6PD to prevent further hemolysis.
Generally, tests will include:
- Complete blood count - Hemoglobin decreases by 3-4 g/dL
- Increased reticulocyte count
- Haptoglobin (decreased in hemolysis)
- Liver enzymes (to exclude other causes of jaundice)
- TSH measurement.
- A "direct antiglobulin test" (Coombs' test) - this should be negative, as hemolysis in G6PD is not immune-mediated
- Since, reticulocytes can have normal G6PD levels, measuring G6PD levels during an acute episode may produce a false-negative result.
Specific tests for G6PD anemia
- Heinz bodies
- Beutler fluorescent spot test
- The Motulsky dye-decolouration test
- Direct DNA testing and/or sequencing of the G6PD gene.
Heinz bodies: Early diagnosis
When a macrophage in the spleen "sees" an RBC with a Heinz body, it removes the precipitate and a small piece of the membrane, leading to characteristic "bite cells". However, if a large number of Heinz bodies are produced, as in the case of G6PD deficiency, some Heinz bodies will nonetheless be visible when viewing RBCs that have been stained with crystal violet. This easy and inexpensive test can lead to an initial presumption of G6PD deficiency, which can be confirmed with the other tests.
Beutler fluorescent spot test: Late diagosis
The Beutler fluorescent spot test is a rapid and inexpensive test that visually identifies NADPH produced by G6PD under ultraviolet light. When the blood spot does not fluoresce, the test is positive; it can be false-positive in patients who are actively hemolysing. It can therefore only be done several weeks after a hemolytic episode.
Bite or Blister cells
- In glucose-6-phosphate dehydrogenase deficiency, "bite" or "blister" cells are produced when accumulated oxidized hemoglobin remains adherent to the erythrocyte membrane, which creates an adjacent membrane-bound clear zone.
Treatment
- In the acute phase of hemolysis, blood transfusions might be necessary. Blood transfusion is an important symptomatic measure, as the transfused red cells are generally not G6PD deficient.
- Dialysis in acute renal failure
- Some patients benefit from removal of the spleen (splenectomy), as this is an important site of red blood cell destruction. * Folic acid should be used in any disorder featuring a high red blood cell turnover.
- Although vitamin E and selenium have antioxidant properties, their use does not decrease the severity of G6PD deficiency.
Primary Prevention
- The most important measure is prevention - avoidance of the drugs and foods that cause hemolysis.
- Vaccination against some common pathogens (e.g. hepatitis A) may prevent infection-induced attacks.
References
- ↑ "The G6PD Deficiency Homepage -- Table 2". Retrieved 2007-10-28.
- ↑ Raupp P, Hassan JA, Varughese M, Kristiansson B (2001). "Henna causes life threatening haemolysis in glucose-6-phosphate dehydrogenase deficiency". Arch. Dis. Child. 85 (5): 411–2. PMID 11668106.
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