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G6PD Deficiency

What is G6PD deficiency?

Glucose-6-phosphate dehydrogenase (G6PD) is an enzyme that helps red blood cells to work properly. Some people have less than the usual amount of G6PD in their red blood cells. This is called G6PD deficiency, or favism.

Most people with G6PD deficiency have completely normal health, but sometimes it can cause problems. This guide explains the problems G6PD deficiency may cause and what to do if your child has problems.

G6PD deficiency is passed on from parents to children

G6PD deficiency is an inherited disorder, which means it is passed from one or both parents to the child. It affects males more often than females.

About 400 million people worldwide have G6PD deficiency. Anyone can have G6PD deficiency, but it is most common in people whose families came from Africa or other areas where malaria has been common, such as the Mediterranean, Caribbean, and South-East Asia. G6PD deficiency is usually milder in people of African origin and more severe in people of Mediterranean and Asian origin.

G6PD protects red blood cells

Red blood cells carry oxygen to all parts of the body. G6PD is an enzyme that helps the red blood cells to function normally. It also helps protect them against substances that can build up when you have a fever or take certain medicines.

If a person does not have enough G6PD, some of their red blood cells may be destroyed when they have a fever or when they take certain medicines. The breakdown of red blood cells is called haemolysis (say: he-MOLL-iss-iss). If this happens, the person may not have enough red blood cells and may become anaemic.

G6PD deficiency can cause problems

Problems for newborn babies

If a mother carries G6PD deficiency, she may pass it on to one or more of her children. Some babies may get jaundiced (yellow) shortly after they are born. This is more likely for baby boys.

Severe jaundice can be serious for newborn babies if it is not treated. It is usually treated by putting the baby under a special light for a few days.

Many babies with G6PD deficiency are diagnosed because they have jaundice soon after birth. Once the jaundice has passed, they should not get other problems from G6PD deficiency, as long as they avoid fava beans and certain medicines.

Problems for children and adults

Most people with G6PD deficiency have completely normal health, but sometimes it can cause problems.

Some children and adults with G6PD deficiency may develop haemolysis and anaemia after they are exposed to any of these triggers:

  • if they get a fever
  • if they take certain medicines listed later in this guide
  • if they eat fava beans; this is called favism

If your child is exposed to a trigger that causes haemolysis, sometimes there are no symptoms at all. In more serious cases, your child may have one or more of the following symptoms of anaemia:

  • pale skin
  • fatigue
  • rapid heartbeat
  • rapid breathing
  • shortness of breath
  • jaundice (yellowing of the skin and eyes)
  • backache
  • dark, tea-coloured urine

If your child is experiencing any of these symptoms, call your family doctor or go to the nearest Emergency Department.

Once the trigger is removed or resolved, the symptoms of G6PD deficiency usually go away fairly quickly, usually within a few weeks.

Your child should not take certain medicines

If your child has G6PD deficiency, he should not take any of the following medicines:

  • acetylsalicylic acid (ASA or Aspirin)
  • ascorbic acid (Vitamin C)
  • chloramphenicol
  • chloroquine
  • dapsone
  • dimercaprol
  • doxorubicin
  • mepacrine
  • methylene blue
  • methyldopa  
  • nalidixic acid
  • naphthalene
  • nitrofurantoin
  • phenazopyridine
  • primaquine
  • quinine
  • sulfacetamide
  • sulfadiazine
  • sulfamethoxazole (Co-trimoxazole, Septra)
  • sulfanilamide
  • sulfapyridine
  • sulfisoxazole (Pediazole)
  • toluidine blue

This list only contains the names of drugs that are more likely to cause haemolysis in patients with G6PD deficiency. The list may change at a later time. Sometimes medicines that are not on this list can also cause problems. Tell your pharmacist, nurse, and doctor that your child has G6PD deficiency and ask them to check before giving your child any medicine, including herbal remedies.

If your child's doctor feels that your child needs to take one of the medicines on the list, your child will have his blood tested while taking the medicine.

The risk and severity of haemolysis is almost always dose-related. This means that if your child takes a higher dose of one of these medicines, he is more likely to develop haemolysis and it is more likely to be severe.

Your child should avoid mothballs and certain foods

Your child should not come in close contact with mothballs (naphthalene).

Your child should not eat fava beans. Some people should also avoid red wine, all beans, blueberries, soya products, tonic water, and camphor.

Key points

  • G6PD is an enzyme that helps protect red blood cells.
  • Most people who have G6PD deficiency are healthy, but sometimes fever or certain medicines and foods can break down their red blood cells (haemolysis) and cause anaemia.
  • Your child with G6PD deficiency should avoid certain medicines and foods.
  • Tell your pharmacist, nurse, and doctor that your child has G6PD deficiency.
  • If your child has symptoms of anaemia, call your family doctor or take your child to the nearest Emergency Department.

Melanie Kirby-Allen, MD, FRCPC

11/6/2009




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