Definition of Glucose-6-phosphate dehydrogenase deficiency:

Glucose-6-phosphate dehydrogenase (G-6-PD) deficiency is a hereditary, sex-linked enzyme defect. It results in the breakdown of red blood cells when the person is exposed to certain drugs or the stress of infection.

Causes, incidence, and risk factors:

The primary effect of G-6-PD deficiency is the reduction of the enzyme G-6-PD in red blood cells, causing destruction of the cells (hemolysis). Ultimately, this hemolysis leads to anemia -- either acute or chronic.

In the United States, many more black than white people have the disorder. Approximately 10 - 14% of the black male population is affected. The disorder may occasionally affect a black women to a mild degree (depending on their genetic inheritance).

The disease also tends to affect people of Middle Eastern decent, particularly Kurdish and those of Sephardic Jewish descent.

People with the disorder are not normally anemic. They do not display any evidence of the disease until the red blood cells are exposed to certain chemicals in food or medicine, or to stress.

Medications that can bring on this reaction include:

• Antimalarial drugs
• Aspirin
• Nonsteroidal anti-inflammatory drugs (NSAIDs)
• Quinidine
• Quinine
• Sulfonamides (antibiotic) Nitrofurantoin

The chronic anemia is unaffected by exposure to these drugs.

Other chemicals, such as those in mothballs, can also bring about hemolysis in people with G-6-PD deficiency. The risk of acute hemolytic crisis can be decreased by reviewing the family history for any evidence of hemolytic anemias or spherocytosis, or testing before giving any medications belonging to the above classes.

The hemolysis episodes are usually brief, because newly produced (young) red blood cells have normal G6PD activity.

Risk factors for G-6-PD deficiency are being black, being male, or having a family history of G6PD deficiency. Another type of this disorder can occur in whites of Mediterranean descent. This form is also associated with acute episodes of hemolysis. Episodes are longer and more severe than in the other types of the disorder.