Glucose-6-Phosphate Dehydrogenase (G6PD) deficiency, also called favism, is a disorder that affects the red blood cells. G6PD is a protein (enzyme) that helps the body's cells function normally. It protects the red blood cells by eliminating substances that could harm them and that are known to induce oxidative stress. G6PD therefore acts like an antioxidant.
Substances that cause oxidative stress include certain medications, foods, chemical substances and infections.
G6PD is an inherited condition, passed along in genes from either one or both parents to the child. Those affected have an abnormality in the gene that controls the production of G6PD, which leads to an inadequate production of the enzyme. The red blood cells, lacking adequate protection, are therefore more susceptible to premature destruction (hemolysis). This may lead to anemia, a term that refers to a decrease in the number of red blood cells.
This deficiency affects between 200 and 400 million people worldwide. It is most prevalent in Africa, the Middle East, Southeast Asia and the Mediterranean. The condition is more common in men (9 times out of 10) than women.
Most people with G6PD deficiency do not have any symptoms. Generally speaking, those affected present symptoms only when exposed to oxidative stress. There are several types of G6PD deficiency. They have different repercussions and differ greatly in severity based on the degree of the gene abnormality.
Symptoms vary according to the type of deficiency. Some individuals will experience episodes of anemia, while others will have more intense or chronic symptoms. Symptoms include:
- Difficulty breathing
- Back and stomach pain
- Jaundice (yellowing of skin and eyes)
- Increased heart rate
- Dark-coloured urine
A more uncommon form of the disorder can cause jaundice in newborns at birth (elevated levels of bilirubin in the blood that can lead to yellowing of the skin).
G6PD deficiency is diagnosed by a blood test. Genetic testing may also be used to determine the type of abnormality. Newborns that belong to any of the higher risk groups mentioned above, or born to a parent affected by the deficiency, are usually screened.
Treatment generally consists in eliminating the oxidative stress responsible for destroying the red blood cells. Treatment will vary according to the agent involved. If an infection is responsible, treating the infection is the first step. However, if it is caused by exposure to a medication, food or chemical substance, the agent in question must be removed immediately. In rare cases, some individuals will require a blood transfusion. As for newborns with jaundice, they are placed under a special light for a few days.
Prevention consists in avoiding factors that may cause oxidative stress such as certain foods, medications and chemical products. Here are a few examples of what should be avoided:
- faba beans, also known as fava or broad beans (legumes)
- naphthalene (mothballs)
- henna dyes
It is very important for close friends and family, as well as health professionals, to be aware of the fact that an individual has G6PD deficiency. Special identification, such as a medical alert bracelet, is useful.
For more information, do not hesitate to speak to your pharmacist.