Glucose-6-phosphate dehydrogenase (G6PD) deficiency is a common enzyme deficiency carried on the X chromosome. It is one of the most common known enzyme deficiencies in the world, found among a wide variety of human populations. People with this genetic condition lack the ability to produce G6PD, and this can lead to problems with the red blood cells. Many people live very active lives with G6PD deficiency, and some are actually unaware that they have a genetic defect until the symptoms manifest.
This enzyme is related to the red blood cells. When a G6PD deficiency is triggered by something like an infection, a certain medication, or a dietary factor, a patient's red blood cell count declines, and hemolytic anemia, in which the bone marrow doesn't make enough red blood cells, can emerge. The patient may experience fatigue, jaundice, dark urine, and unusually pale skin when the deficiency becomes acute. Patients can also experience chronic low-level anemia as a result of this enzyme deficiency.
People of African and Mediterranean descent seem to be especially at risk of G6PD deficiency. Intriguingly, people with this deficiency are more resistant to malaria, especially life-threatening strains, which is a definite advantage, since individuals with a G6PD deficiency usually cannot take antimalarial drugs. The fact that malaria is endemic in African and the Mediterranean probably has something to do with the frequency of G6PD deficiency in these areas, as a natural resistance to malaria would have been a distinct advantage for humans in these areas historically.
For people who are interested, this enzyme deficiency can be identified with a blood test. People who think that they might be at risk can opt for a blood test to look for G6PD deficiency before it becomes a problem, and parents may also ask for the test to determine whether or not their children have inherited the gene. Testing may also be performed when a patient presents with the signs of an acute deficiency, as might happen when a child takes antibiotics for the first time and gets very sick as a result of the deficiency.
In individuals with G6PD deficiency, it is necessary to avoid triggers, such as certain medications and types of infections. Vaccinations are often strongly recommended so that people will not get sick with infections which could cause acute symptoms. Many patients also need to steer clear of fava beans, as G6PD deficiency is closely related to favism, a common inherited condition in the Mediterranean characterized by the inability to eat fava beans. Mothballs can also trigger acute reactions.
