Glucose-6-phosphate-dehydrogenase (G6PD) deficiency is an inherited disease that can cause anemia, or a low red blood cell count.
What is going on in the body?
G6PD deficiency occurs when a person doesn't have enough of an enzyme called glucose-6-phosphate-dehydrogenase. This enzyme is important in metabolism. Red blood cells, which carry oxygen, don't get enough energy when G6PD is lacking. The red blood cells die too soon in this condition, which can cause anemia. Anemia can be mild or severe and is often triggered suddenly by illness, foods, or certain medications.
What are the causes and risks of the disease?
G6PD deficiency is inherited on the X chromosome.
Females have two X chromosomes but males have one X and one Y chromosome. This disease is therefore called "X-linked" and usually only occurs in men. This is because men only need to inherit one abnormal gene to get the disease. Women, on the other hand, have to inherit two abnormal genes to get the disease.
In the US, a mild form of G6PD deficiency is very common in blacks. Those from the eastern Mediterranean region are at a higher risk for a more severe form of G6PD deficiency.
Sudden attacks of G6PD deficiency, or a hemolytic crisis, can be caused by:
- any serious illness
- fava beans, in the more rare forms of G6PD deficiency
- sulfa medications, such as sulfamethoxazole, an antibiotic
- certain medications used to treat malaria, such as primaquine
- nitrofurantoin (i.e., Macrobid, Macrodantin), an antibiotic
- aspirin, which doesn't usually cause a problem in people with the common form of G6PD deficiency
What can be done to prevent the disease?
G6PD deficiency is an inherited disease, so it cannot be prevented. Genetic counseling may be helpful to couples with a family history of the disease.
How is the disease diagnosed?
The diagnosis of G6PD deficiency is suspected when jaundice and anemia occur. Blood tests, including a complete blood count or CBC and a blood chemistry tests, are done to show that red blood cells have died in large numbers.
A specific diagnosis can be made by measuring of the amount of G6PD enzyme activity in red blood cells. This blood test can tell whether the amount of G6PD is abnormally low.
In some cases, a blood test called protein electrophoresis may need to be done to confirm the diagnosis.
Long Term Effects
What are the long-term effects of the disease?
Some people may have a mild form of G6PD deficiency with no long-term effects.
Children with severe forms of this disease may have growth problems. These children may need constant monitoring and treatment. Some long-term problems include an enlarged spleen or liver and the need for blood transfusions.
Severe, sudden attacks of red cell breakdown can result in kidney damage, congestive heart failure, shock, and even death. This is uncommon in the variety of G6PD deficiency seen in the US. Most affected people in the US can lead a normal life if they are able to avoid the medications and illnesses that cause sudden red blood cell death.
What are the risks to others?
G6PD deficiency is not contagious, but an abnormal G6PD gene can be passed on to children, who may or may not get the disease.
What are the treatments for the disease?
Most people with G6PD deficiency do not need regular treatment. The genetic defect cannot be cured. If a hemolytic crisis occurs, a person usually needs short-term treatment. If a medication caused the attack, the person should stop taking that medication right away.
Other treatment is directed at the person's needs. This may include oxygen, fluids, or medications to treat problems such as congestive heart failure or chronic renal failure. Blood transfusions may be needed in some cases.
Some people may need surgery to have their spleen taken out if it gets too big. A treatment called iron chelation therapy may be needed if iron overload occurs. This therapy helps the body get rid of excess iron. These treatments help with complications of G6PD deficiency, but they do not fix or cure the disease.
What are the side effects of the treatments?
Blood transfusions may cause allergic reactions or infections. Having many transfusions can lead to infections. It may also lead to iron overload, a condition in which there is too much iron in the body. Surgery carries a risk of bleeding, infection, or allergic reaction to the anesthesia. Iron chelation therapy may cause allergic reactions and stomach upset.
What happens after treatment for the disease?
Most affected people in the US have mild forms of G6PD deficiency. These people often need no treatment other than to avoid certain medications. When they become ill, closer monitoring or treatment may be needed. Those with severe forms of G6PD deficiency often need close monitoring and treatment for life.
How is the disease monitored?
G6PD deficiency is monitored with blood tests, such as CBC and blood chemistry tests. These can detect anemia or blood cell death and response to therapy. The disease does not generally get worse or improve with age. Any new or worsening symptoms should be reported to the healthcare professional.
Harrison's Principles of Internal Medicine, 1998, Fauci et al.