G6PD Deficiency

What is G6PD deficiency?

Glucose 6-phosphate dehydrogenase (G6PD) deficiency is an enzyme deficiency of the red blood cells. G6PD deficiency leads to an abnormal rupture (breakage) of the red blood cells called hemolytic anemia (abnormally low red blood cell count).

G6PD deficiency is the most common known human enzyme disease, affecting 10% of the world's population.

What is the cause of G6PD deficiency?

The abnormal gene responsible for this inherited enzyme deficiency is located on the X-chromosome. Therefore, the illnesses associated with G6PD deficiency occur more frequently in males than females, since males only have one X-chromosome. There are different degrees of G6PD deficiency, which vary according to the magnitude of the missing enzyme.

G6PD deficiency occurs more frequently in African Americans, Italians, Greeks, Asians, and other Mediterranean peoples.

The degree of red blood cell rupture (hemolysis) varies according to the degree of enzyme deficiency and the drug exposure. Usually, the hemolytic anemia occurs after exposure to certain compounds with oxidant properties, including drugs such as malaria medications (such as primaquine and hydroxychloroquine), sulfonamides, antiitching drugs, dapsone, and others. Compounds with the property of inducing hemolysis in G6PD deficient persons are also found in the fava bean. This condition, known as favism, occurs within a day of ingestion of the fava bean. Favism can cause fever, back pain, headache, nausea, and chills.

Infections, such as pneumonia, can also precipitate the hemolytic anemia in persons who are G6PD deficient.

How is G6PD deficiency diagnosed?

Patients with G6PD deficiency and hemolytic anemia can develop jaundice (yellowing of the eyes). Sometimes jaundice can occur in newborn babies who are G6PD deficient.

The diagnosis is made by blood testing which can demonstrate the inadequate levels of the G6PD enzyme activity by blood testing.

What is the treatment for G6PD deficiency?

Treatment of G6PD deficiency involves discontinuing the offending drug or compound and treating any accompanying infection. Recovery is the rule. Sometimes blood transfusions are needed when the anemia is severe.

Reference: Harrison's Principles of Internal Medicine, McGraw-Hill, edited by Eugene Braunwald, et. al., 2001.

Last Editorial Review: 12/7/2005

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