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| ==Overview== | | ==Overview== |
| '''Glucose-6-phosphate dehydrogenase (G6PD) deficiency''' is an [[Sex-linked|X-linked recessive]] [[hereditary disease]] featuring abnormally low levels of the [[G6PD]] enzyme, which plays an important role in [[red blood cell]] function. Individuals with the disease may exhibit non-immune [[hemolytic anemia]] in response to a number of causes. It is closely linked to '''[[favism]]''', a disorder characterized by a hemolytic reaction to consumption of [[Vicia faba|broad bean]]s, with a name derived from the [[Italian language|Italian]] name of the broad bean (''fava''). Sometimes the name, [[favism]], is alternatively used to refer to the enzyme
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| deficiency as a whole.
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| ==Laboratory 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.
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| Generally, tests will include:
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| * [[Complete blood count]] - Hemoglobin decreases by 3-4 g/dL | |
| * Increased [[reticulocyte]] count
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| * [[Haptoglobin]] (decreased in hemolysis)
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| * [[Liver enzyme]]s (to exclude other causes of [[jaundice]])
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| * [[Thyroid-stimulating hormone|TSH]] measurement.
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| * A "[[Coombs test|direct antiglobulin test]]" (Coombs' test) - this should be negative, as [[hemolysis]] in G6PD is not immune-mediated
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| * Since, reticulocytes can have normal G6PD levels, measuring G6PD levels during an acute episode may produce a false-negative result.
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| ===Specific tests for G6PD anemia===
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| * [[Heinz body|Heinz bodies]]
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| * Beutler fluorescent spot test
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| * The Motulsky dye-decolouration test
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| * Direct DNA testing and/or sequencing of the G6PD gene.
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| ====Heinz bodies: Early diagnosis====
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| 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 [[RBC]]s 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.
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| ====Beutler fluorescent spot test: Late diagosis====
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| The '''Beutler fluorescent spot test''' is a rapid and inexpensive test that visually identifies [[Nicotinamide adenine dinucleotide phosphate|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.
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| ====Bite or Blister cells====
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| * 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.
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| ==References== | | ==References== |