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G-6-PD Deficiency (G-6-PD)
Sunday, 27 July 2003
Monday, 29 November 2004
Glucose-6-Phosphate Dehydrogenase Deficiency


Glucose-6-Phosphate Dehydrogenase (G-6-PD) deficiency is a hereditary enzyme deficiency of the red blood cells that predisposes the individual to developing hemolytic anemia. G-6-PD is an enzyme or protein involved in energy metabolism in red blood cells (RBCs) and is necessary for the prevention of cell damage. The activity of G-6-PD is highest in young RBCs and decreases with cell aging. A deficiency of this protein is one of the most common genetic abnormalities known, affecting over 400 million people worldwide. Interestingly, this mutation has the benefit of conferring resistance to malaria. Some G-6-PD deficient individuals are also allergic to fava beans (see “additional resources” #5).


Although distribution of the mutant gene for G-6-PD deficiency is worldwide, the highest incidence occurs in the darkly pigmented racial and ethnic groups, such as those of African, Asians and Mediterranean ancestry. In the United States, it affects about 10% of African American males. Because the defective gene is carried on the X chromosome, it is passed from mother to son and the condition is more common in men. In women, full expression of the disorder only occurs when a mutant gene on both X chromosomes is inherited.

Signs and Symptoms

The majority of individuals with G-6-PD deficiency has no symptoms at all and is not even aware of their genetic trait. This is because enzymatic activity as low as 20% of normal is still sufficient for normal function of red blood cells. In newborns, jaundice (yellow skin pigmentation) is often observed. Otherwise, older individuals appear normal. It is not until the development of infection or the administration of certain drugs or foods that stress the red blood cell that the G-6-PD deficient RBCs are prone to hemolysis or destruction. The result is a hemolytic anemia, often associated with symptoms of fatigue, shortness of breath, rapid heart rate, enlarged spleen and pale color. In addition, jaundice, dark urine, and increased blood concentrations of by-products from red blood cell destruction may also be observed. The percentage of immature red blood cells, called reticulocytes, may be increased as the body attempts to replace the lost cells. Some individuals may also complain of abdominal or back pain.

Possible Causes

G-6-PD deficiency occurs from the transmission of a defective gene located on the X chromosome. Conditions exhibiting this mode of inheritance are termed “sex-linked.” There are over 400 variants of the G-6-PD enzyme and these have been classified into approximately 50 different gene mutation groups.


Several blood tests detect hemolytic anemia. These include a low RBC count and low hemoglobin concentrations, elevated levels in the blood of by-products of RBC destruction, and a peripheral blood smear, which presents a “picture” of the red blood cells. G-6-PD activity level in RBCs can be tested in the laboratory from a blood sample and is necessary in order to make the diagnosis.


The course of action depends on the severity of symptoms, which varies based on the type of mutation. In most cases, treatment involves restricting exposure to agents that cause hemolysis. Often, this consists of stopping the administration of the offending drug or eating the foods known to cause hemolysis. In cases of severe hemolytic anemia, blood transfusions may be necessary.


The long-term outcome is usually very good. Early diagnosis and treatment eliminate symptoms and help prevent recurrent crises of hemolytic anemia. For the majority of individuals with mild symptoms, avoidance of triggering factors allows them to lead normal, healthy lives. Screening of family members of patients with G-6-PD deficiency may be helpful in order to provide genetic counseling to females who carry the gene and to males who are affected but do not have symptoms.

Connect with other parents

In the spirit of community and support, Madisons Foundation offers the unique service of connecting parents of children with rare diseases. If you would like to be connected to other parents of children with this disease, please fill out this brief form.


Kids Health
This is an excellent site providing a wealth of information to young patients and their parents. The information is thorough and detailed yet written in even a child-friendly format. It is a great educational resource for learning about G-6-PD deficiency.

An Introduction to G6-PD Defiency
This is a very good site offering comprehensive information on the scientific aspect of G-6-PD deficiency. It has a valuable list of contents and various links.

Medline Plus
This site offers an easy to read overview of the condition with definitions of technical terms.
This site has a link to a brochure that includes lists of medications that are safe to take and to avoid, respectively.

Google Search for G-6-PD Deficiency (G-6-PD)

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