A genetic deficiency that can lead to anemia
Glucose-6-phosphate dehydrogenase (G6PD) is a substance that helps the body use sugar for energy. It is an enzyme, which means it speeds up chemical changes when the body converts sugar to energy.
The G6PD enzyme is found in all the body’s cells, but it is especially important in red blood cells. These are the cells that contain hemoglobin and carry oxygen throughout the body. The G6PD enzyme protects the red blood cells from harmful chemicals or toxins, which can build up in your body during certain illnesses or after taking some medicines.
People with G6PD deficiency do not have enough G6PD enzyme to neutralize certain chemicals or toxins. Normally, there are only tiny amounts of toxins in the body, and so it is not usually a problem for the G6PD enzyme to make them harmless.
So, what is the problem?
If G6PD is not present, strong chemical products are not neutralized and they can damage the hemoglobin inside red blood cells. A build-up of toxins or chemicals can cause the red blood cells to break apart and be destroyed (also known as hemolysis). This makes a person anemic (reduced levels of hemoglobin and red blood cells). Sometimes the anemia can happen very quickly.
Hemolysis may lead to severe anemia and can cause jaundice (a yellowing of the skin) from the build-up of hemoglobin breakdown products in the blood. Some infants who experience jaundice have G6PD deficiency.
The IHTC clinical team will provide a detailed list of medicines and substances that are known to “trigger” hemolysis and which should be avoided. Fortunately, once the cause or trigger is removed, hemolysis usually stops within a short period of time.
Cause of G6PD Deficiency
G6PD deficiency is a genetic condition that is caused by an alteration (a mutation or a change) in the G6PD gene. This mutation prevents the production of the normal enzyme. The mutation is passed on in families in an X-linked recessive pattern. This means that the gene that codes for the G6PD enzyme is located on the X-chromosome; males have one X chromosome and females have two. When a male inherits a gene for G6PD that is not functioning properly, he will have G6PD deficiency. When a female inherits a gene for G6PD deficiency she is referred to as a carrier because she has a second normal copy of the gene (from the other parent) that can often compensate for the altered gene. Female carriers may or may not experience symptoms of G6PD deficiency.
Carriers of G6PD deficiency have a 50% chance of passing the altered gene on to each of their children. Each son of a carrier has a 50% chance of having G6PD deficiency and each daughter has a 50% chance of being a carrier. Men with G6PD deficiency do not pass the gene on to any of their sons; however, all of their daughters will be carriers. Often a mother has no symptoms and has no way of knowing that she is a carrier of G6PD deficiency. Carrier testing in families who are known to have G6PD deficiency is available at the IHTC if desired.
G6PD deficiency can occur in a person from any ethnic group. In the United States it is most commonly found in people of African American, Mediterranean (Italian or Greek), Southeast Asian, or Middle Eastern descent.
Diagnosis of G6PD Deficiency
The only way to know if a person has G6PD deficiency is to perform a special blood test as G6PD deficiency does not usually cause problems, except in rare circumstances (see section below under “chronic hemolysis”). Many people can go through life without any symptoms. It only becomes a problem if the person is exposed to certain chemical compounds or toxins, or experiences certain infections that can cause hemolysis.
People with G6PD deficiency have an increased risk of hemolysis and severe anemia if they have certain infections such as Fifth disease (parvovirus), infectious hepatitis, infectious mononucleosis (mono), pneumonia, or a blood infection.
In some people with G6PD deficiency, a small amount of red blood cell destruction occurs all the time. This process is known as “chronic hemolysis”.
Usually a person with chronic hemolysis makes more than the average amount of red blood cells to make up for the ones that are being constantly destroyed. This increased rate of red blood cell production can be measured using a blood test called a reticulocyte (or “retic”) count. The retic count is usually elevated in a person with chronic hemolysis. This means the body is keeping up with the demands for red blood cells and hemoglobin.
For persons with the form of G6PD deficiency that is associated with chronic hemolysis, their doctor may prescribe a medication called folic acid. This vitamin supplement helps the bone marrow keep up with the increased production demands needed to make the extra red blood cells. The symptoms of hemolysis and the resulting anemia may include tiredness, paleness, headache, yellow tint to the whites of the eyes or skin (jaundice or icterus), fast heartbeat, shortness of breath, or dark urine (tea or coke colored). Individuals with these symptoms should inform their healthcare provider promptly.
Special Considerations: What to Avoid
You cannot prevent G6PD deficiency, but fortunately, if you avoid exposure to certain medicines and foods, you can prevent the more serious symptoms. Fava beans is one of the foods you should always avoid.
Medications: What to Take, What to Avoid
Any time persons with G6PD take any medication, whether prescribed by a doctor or over-the-counter, they should tell their doctor or pharmacist that they have G6PD deficiency to be sure that it is safe to take the medication.
The common over-the-counter treatments for fever, pain, nasal congestion and cough – acetaminophen (Tylenol), ibuprofen (Advil), pseudoephedrine (Sudafed), and guaifenesin, (Robitussin) – are usually safe at normal therapeutic doses for people with G6PD deficiency. People with G6PD deficiency should avoid medicines that contain aspirin (salicylic acid).
Common Over-the-Counter Medications to AVOID:
- Pepto Bismol
Common Prescription drugs to AVOID:
- Chloroquine (Aralen)
- Mefloquine (Lariam)
Sulfonamides and Sulfones:
- Furosemide (Lasix)
- Sulfacetamide (Sulamyd)
- Sulfamethoxazole (Bactrim, Septra)
- Sulfasalazine (Azulfidine)
- Sulfisoxazole (Gantrisin)
- Nitrofurantoin (Furadantin, Macrobid, Macrodantin)
Quinolones and Fluoroquinolones:
- Ciprofloxacin (Cipro)
- Levofloxacin (Levaquin)
- Moxifloxacin (Avelox, Vigamox)
- Norfloxacin (Noroxin)
Other products to AVOID:
- Fava beans (a type of bean found in the Mediterranean)
- Glyburide (Diabeta)
- Methylene Blue (a dye)
- Moth balls (or anything containing naphthalene)
- Nitrofurazone (Furacin)
- Rasburicase (Elitek)
- Tolbutamide (Orinase)
- Toluidine Blue (a dye)
Learn about all the foods and medications to avoid
How the IHTC can help you
The IHTC is committed to providing expert care for infants, children, teens, and adults with G6PD. As a center of excellence in the treatment of bleeding and clotting disorders, the IHTC offers a high level of coordinated care for patients with this disorder. We also provide prompt communication with your local healthcare provider related to our treatment plan and your progress. The IHTC team collaborates with national experts and patient participation in research studies may be available.
At the IHTC we have clinicians who are experts in treating G6PD and providing support to patients with this disorder. As patients with G6PD must avoid certain foods and medicines, it is very important that you are seen by a clinician who is familiar with the signs and treatment of G6PD. We can help you with diagnosis, testing and treatment; and can provide expert dietary guidance suitable for your specific needs.
For more information, please contact the IHTC.