G6PD deficiency

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what is Glucose-6-phosphate dehydrogenase deficiency


• X-linked recessive hereditary disease  (penyakit keturunan)
• characterised by abnormally low levels of glucose-6-phosphate dehydrogenase (abbreviated G6PD or G6PDH), a metabolic enzyme involved in the pentose phosphate pathway, especially important in red blood cell metabolism.

• Individuals with the disease may exhibit nonimmune hemolytic anemia in response to a number of causes, most commonly infection or exposure to certain medications or chemicals.

• Is closely linked to favism, a disorder characterized by a hemolytic reaction to consumption of broad beans,

 All mutations that cause G6PD deficiency
• are found on the long arm of the X chromosome, on band Xq28.
• The G6PD gene spans some 18.5 kilobases.[3]

Signs /symptoms

• Most individuals with G6PD deficiency are asymptomatic.

• Symptomatic patients are almost exclusively male, due to the X-linked pattern of inheritance,

• but female carriers can be clinically affected due to unfavorable Lyonization, where random inactivation of an X-chromosome in certain cells creates a population of G6PD-deficient red blood cells coexisting with normal red cells.

• Abnormal red blood cell breakdown (hemolysis) in G6PD deficiency can manifest in a number of ways:

-Prolonged neonatal jaundice, possibly leading to kernicterus (arguably the most serious complication of G6PD deficiency)

• Hemolytic crises in response to: (perkara perkara yang menyebabkan pengidap g6pd deficiency lebih teruk)

-Illness (especially infections)

-Certain drugs (see below)

-Certain foods, most notably broad beans

-Certain chemicals

-Diabetic ketoacidosis

• Very severe crises can cause acute renal failure

Many substances are potentially harmful to people with G6PD deficiency, variation in response to these substance makes individual predictions difficult.

• Antimalarial drugs that can cause acute haemolysis in people with G6PD deficiency include ¬¬-primaquine, pamaquine and chloroquine.

• -There is evidence that other antimalarials may also exacerbate G6PD deficiency, but only at higher doses.

• Sulfonamides (such as sulfanilamide, sulfamethoxazole and mafenide), thiazolesulfone, methylene blue and naphthalene should also be avoided by people with G6PD deficiency, as should

• certain analgesics (such as aspirin, phenazopyridine and acetanilide) and

• a few non-sulfa antibiotics (nalidixic acid, nitrofurantoin, and furazolidone).[1][3][4]

• Henna has been known to cause haemolytic crisis in G6PD-deficient infants.[5]

Diagnosis

The diagnosis is generally suspected when patients from certain ethnic groups (see epidemiology) develop anemia, jaundice and symptoms of hemolysis after challenges from any of the above causes, especially when there is a positive family history.

Generally, tests will include:

• Complete blood count and reticulocyte count; in active G6PD, Heinz bodies can be seen in red blood cells on a blood film;

• Liver enzymes (to exclude other causes of jaundice);

• Lactate dehydrogenase (elevated in hemolysis and a marker of hemolytic severity)

• Haptoglobin (decreased in hemolysis);

• A "direct antiglobulin test" (Coombs' test) - this should be negative, as hemolysis in G6PD is not immune-mediated;

• When there are sufficient grounds to suspect G6PD, a direct test for G6PD is the "Beutler fluorescent spot test", which has largely replaced an older test (the Motulsky dye-decolouration test).

• Other possibilities are direct DNA testing and/or sequencing of the G6PD gene.

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 falsely negative in patients who are actively hemolysing. It can therefore only be done 2-3 weeks after a hemolytic episode.