G6PD deficiency (Fava bean sensitivity)

G6PD deficiency (Fava bean sensitivity)

Often, before I prescribe a drug to a young patient, his/her mother will tell me “But doctor, he is sensitive to fava beans”. I think it is really important for parents to inform me of this, even though in 99.9% of cases, it doesn’t make a difference.

What does having fava beans sensitivity actually mean? What should patients with such sensitivity be aware of? And how can one test for the presence of G6PD deficiency?

What is G6PD deficiency/fava bean sensitivity?

G6PD stands for Glucose-6-phosphate Dehydrogenase, which is the full name for one of the enzymes responsible for maintaining the stability of red blood cells.

G6PD deficiency is the most common enzyme deficiency in humans.

In which groups of people is it more common?

This enzyme deficiency can be seen in people worldwide but it is more common in Middle-Easterns, Asians and Africans.

There are about 400 different genetic mutations that can lead to this enzyme deficiency and there are many different subtypes of G6PD deficiency, each with different levels of severity. In some of the cases there isn’t a real enzyme deficiency but just a reduction in its activity.

The gene for this enzyme can be found on chromosome X and since males only have one X chromosome this naturally means that most of the people with this enzyme deficiency are males. However, this deficiency can also be seen in women, especially in populations with high prevalence.

What does G6PD deficiency cause?

This defect has very little significance on the daily life of people who suffer from it. However, at times of bodily stress, including exposure to certain drugs or fava beans, their red blood cells are destroyed (hemolysis).

How is G6PD deficiency diagnosed?

G6PD enzyme deficiency can be diagnosed with the help of a very simple blood test. In some countries in the world, this test is part of standard newborn screening. However, in the United States, screening for this disorder is not part of standard practice.

So. should all children get tested for G6PD deficiency?

I don’t think parents should rush to see their doctor and request a blood test for their child unless he/she has a reason to suspect that their child may have it (such as family history and/or ethnic background).

What are the clinical manifestations of G6PD deficiency?

In most cases, there are no clinical manifestations at all.

At times of physical bodily crises (such as fever or infection), exposure to drugs or fava beans may lead to destruction of red blood cells which could bring about anemia, dark urine and jaundice.

Children, especially those under 5 years of age, are more prone to crises after exposure to fava beans.

In newborns, G6PD deficiency can lead to severe jaundice after birth.

Do you have to actually eat the fava beans in order to develop a hemolytic crisis?

Unfortunately, consumption isn’t necessary. Inhalation of steam produced when fava beans are being cooked or walking past a fava bean field alone may be enough to cause hemolysis.

So, what do you as parents need to do?

  1. Find out the G6PD status of your child, if it was tested.
  2. Parents who already know that they or their child have G6PD deficiency should avoid exposure to fava beans or naphthalene.
  3. Parents who know that they or their child have G6PD deficiency should avoid certain drugs (mentioned below).
  4. Parents should always make sure their doctor knows that their child has G6PD deficiency before he writes a prescription for any sort of injection or drug.
  5. During an infectious disease, parents should be aware of the presence of pallor in their children, especially in the first few days of the illness. If you suspect your child is pale, take him to the doctor.
  6. In cases of exposure to any of the prohibited drugs or substances, see your doctor.

Which drugs are not allowed in people with G6PD deficiency?

Due to the fact that there are many sub-types of G6PD deficiency, in different population, you should follow your local health service recommendations.

However, I have listed below the recommendation of the Israeli ministry of health drugs, in their order of frequency of usage.

Phenozoypyridine – a drug that is used to relieve symptoms of urinary tract infection.

Nitrofurantoin – an antibiotic used for prevention and treatment of urinary tract infection in all ages.

Primaquin – a drug used for prevention and treatment of malaria.

Rasburicase – a drug infrequency used, its use is mainly limited to cancer patients.

Methylene blue – a drug that is quite rarely used and is needed in rare diseases such as methemoglobinemia.

Avlosulfon – a drug that is also quite rarely used and is needed for exotic diseases such as leprosy.

Toluidine blue – infrequently used, needed for thyroid gland imaging.

Additional drugs that should be avoided include: acetanilid, phenylhydrazine, niridazole and sulfapyridine.

Which drugs are allowed for people with G6PD deficiency?

Pretty much any drugs that I haven’t listed above, including paracetamol, aspirin, vitamin C, synthomycine, chloroquine (as a single treatment regimen) Sulfamethoxazole and trimethoprim (regular dosing).

Remember, in the past they used to think that lots of different drugs were dangerous for people with G6PD deficiency and so many members of the older generation still think that drug such as aspirin, are to be avoided. Today we know that the list of drugs that should be avoided is actually quite short and limited.

What about breastfeeding mothers?

If a mother who doesn’t have G6PD deficiency is breastfeeding a baby who was found to have the enzymatic deficiency, she is to avoid the drugs mentioned above throughout the breastfeeding period and also avoid exposure to fava beans.

To summarize, I think this is a topic that is worth being familiar with. It is important to know your child’s G6PD status and to inform your doctor of his status prior to starting any drug.

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