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Glucose-6-phosphate dehydrogenase deficiency

What is glucose-6-phosphate dehydrogenase deficiency?

Glucose-6-phosphate dehydrogenase deficiency is a genetic disorder that occurs most often in males. This condition mainly affects red blood cells, which carry oxygen from the lungs to tissues throughout the body. In affected individuals, a defect in an enzyme called glucose-6-phosphate dehydrogenase causes red blood cells to break down prematurely. This destruction of red blood cells is called hemolysis.

The most common medical problem associated with glucose-6-phosphate dehydrogenase deficiency is hemolytic anemia, which occurs when red blood cells are destroyed faster than the body can replace them. This type of anemia leads to paleness, yellowing of the skin and whites of the eyes (jaundice), dark urine, fatigue, shortness of breath, and a rapid heart rate. In people with glucose-6-dehydrogenase deficiency, hemolytic anemia is most often triggered by bacterial or viral infections or by certain drugs (such as some antibiotics and medications used to treat malaria). Hemolytic anemia can also occur after eating fava beans or inhaling pollen from fava plants (a reaction called favism).

Glucose-6-dehydrogenase deficiency is also a significant cause of mild to severe jaundice in newborns. Many people with this disorder, however, never experience any signs or symptoms.

How common is glucose-6-phosphate dehydrogenase deficiency?

An estimated 400 million people worldwide have glucose-6-phosphate dehydrogenase deficiency. This condition occurs most frequently in certain parts of Africa, Asia, and the Mediterranean. It affects about 1 in 10 African-American males in the United States.

What genes are related to glucose-6-phosphate dehydrogenase deficiency?

Mutations in the G6PD gene cause glucose-6-phosphate dehydrogenase deficiency.

The G6PD gene provides instructions for making an enzyme called glucose-6-phosphate dehydrogenase. This enzyme is involved in the normal processing of carbohydrates. It also protects red blood cells from the effects of potentially harmful molecules called reactive oxygen species. Reactive oxygen species are byproducts of normal cellular functions. Chemical reactions involving glucose-6-phosphate dehydrogenase produce compounds that prevent reactive oxygen species from building up to toxic levels within red blood cells.

If mutations in the G6PD gene reduce the amount of glucose-6-phosphate dehydrogenase or alter its structure, this enzyme can no longer play its protective role. As a result, reactive oxygen species can accumulate and damage red blood cells. Factors such as infections, certain drugs, or ingesting fava beans can increase the levels of reactive oxygen species, causing red blood cells to be destroyed faster than the body can replace them. A reduction in the amount of red blood cells causes the signs and symptoms of hemolytic anemia.

Researchers believe that carriers of a G6PD mutation may be partially protected against malaria, an infectious disease carried by a certain type of mosquito. A reduction in the amount of functional glucose-6-dehydrogenase appears to make it more difficult for this parasite to invade red blood cells. Glucose-6-phosphate dehydrogenase deficiency occurs most frequently in areas of the world where malaria is common.

How do people inherit glucose-6-phosphate dehydrogenase deficiency?

This condition is inherited in an X-linked recessive pattern. A condition is considered X-linked if the mutated gene that causes the disorder is located on the X chromosome, one of the two sex chromosomes. In males (who have only one X chromosome), one altered copy of the gene in each cell is sufficient to cause the condition. In females (who have two X chromosomes), a mutation must be present in both copies of the gene to cause the disorder. Males are affected by X-linked recessive disorders much more frequently than females. A striking characteristic of X-linked inheritance is that fathers cannot pass X-linked traits to their sons.

Glucose-6-Phosphate Dehydrogenase Deficiency on Wikipedia

'''Glucose-6-phosphate dehydrogenase (G6PD) deficiency''' is an Sex-linked hereditary disease featuring nonimmune hemolytic anemia in response to a number of causes. Its classic association to consumption of Vicia fabas and is commonly known as '''favism''' from the Italian language name of the broad bean ''fava''.

Signs and symptoms

Patients are almost exclusively male, due to the X-linked pattern of inheritance, but female carriers can have a mild form of G6PD. G6PD manifests itself in a number of ways: * Prolonged jaundice#neonatal_jaundice * Hemolysis crises in response to: ** Certain medication (see below) ** Certain foods, most notably Vicia fabas ** Illness (severe infections) * Very severe crises can cause acute renal failure Drugs that have been linked to G6PD: * Primaquine (an malaria) * 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) * Several others[http://www.rialto.com/g6pd/table2.htm]

Diagnosis

The diagnosis is generally suspected when patients from certain ethnic groups (see below) develop anemia, jaundice and symptoms of hemolysis after challenge to any of the above causes, especially when there is a positive family history. Generally, tests will include: * Full blood count and reticulocyte count; in active G6PD, "Heinz bodies" (aggregates of protein) can be seen in red blood cells on a blood film; * Liver enzymes (to exclude other causes of jaundice); * Haptoglobin (decreased in hemolysis); * A "Coombs test" (Coombs' test) - this should be negative, as hemolysis in G6PD is not immune-mediated; * Thyroid-stimulating ...   [ Read More ]


External Resources

Favism - Information on this disorder, Glucose-6-Phosphate Dehydrogenase enzyme deficiency. Including lists of drugs and food to avoid, medical articles, and related links.


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