G6PD deficiency (favism)

Causes and who gets it

G6PD deficiency is inherited, which means it is passed down from parents; it is not contagious. The gene that makes the enzyme is on the X chromosome. Males have only one X chromosome, so a single change in this gene usually causes the deficiency. This is why males are affected more often. In males there is no in-between carrier state: the enzyme is either normal or clearly low. Fathers cannot pass this gene to their sons.

Girls have two X chromosomes. Girls with one changed copy are carriers; most have no symptoms or only mild ones. But in each cell one of the two X chromosomes is randomly switched off, so in some girls the enzyme level can be as low as in males, and the same attacks can happen. In short, being a carrier does not always mean having no symptoms.

The chance is higher if G6PD deficiency runs in your family. The Mediterranean type, the most common type in Europe and in West and Central Asia, is one of the forms of the enzyme deficiency that can be more severe.

Symptoms

Without contact with a trigger, most people have no symptoms. When red blood cells break down quickly, the following may appear:

• Sudden paleness, weakness and tiredness
• Yellowing of the skin and the whites of the eyes (jaundice)
• Urine the color of dark tea or cola, reddish or almost black
• Shortness of breath, fast heartbeat, dizziness
• Fever, back or belly pain

Breakdown triggered by a medicine often becomes noticeable a day or two after you start taking it. Once the trigger is removed, the attack often settles on its own, because the body makes new red blood cells to replace them. In the Mediterranean type, however, the breakdown may continue as long as the trigger continues. Rarely, severe breakdown can lead to kidney failure and can be life-threatening.

In newborns, G6PD deficiency is one of the important causes of jaundice, which can range from mild to severe.

Diagnosis and tests

The diagnosis is made with a blood test that measures the level of the G6PD enzyme. A few drops of blood are taken from the arm in adults and from the heel in babies; no special preparation is needed. To see how much breakdown there is, your doctor may also order tests such as a complete blood count, a reticulocyte (young red blood cell) count, bilirubin, LDH and hemoglobin in the urine.

If the test was done during an attack, the result can be misleading; in that case your doctor may repeat the test a few weeks later. In women, the result may come out slightly low; this often shows carrier status, and your doctor interprets it.

In babies, this test may be ordered if jaundice lasts longer than two weeks, cannot be explained by another cause, or if there is G6PD deficiency in the family.

Treatment approach

The basis of treatment is staying away from triggers. During an attack, the doctor first finds the cause. A medicine causing the breakdown is stopped, and an infection, if present, is treated. Most attacks settle on their own as the body makes new red blood cells. If the anemia is severe, a blood transfusion may be needed.

For newborn jaundice, light treatment (phototherapy) is used most often when needed; rarely, a blood transfusion or a medicine given into a vein is needed. If you think a medicine prescribed to you may be risky, do not decide on your own; ask your doctor or pharmacist right away.

Everyday life and follow-up

The most important rule for living with G6PD deficiency is to know your triggers and stay away from them.

• Do not eat fava beans. The substances that make fava beans harmful are not destroyed by cooking. Breathing in the pollen of the fava bean plant can also trigger an attack.
• Read labels on ready-made foods and plant-based meat products; avoid those that contain fava bean protein. When eating out, ask whether a dish contains fava beans.
• It is safest not to use mothballs at home. Air clothes and blankets stored with mothballs outdoors and wash them before using them.
• Before any new medicine, including over-the-counter medicines, tell your doctor, pharmacist and dentist that you have G6PD deficiency.
• Carry a list of the medicines and substances you need to avoid, prepared with your doctor, in your wallet and on your phone.
• Infections are the most common trigger; watch your symptoms closely during an illness with fever.

Some medicines and groups of medicines worth knowing about for your safety are listed below. The list is not complete; your doctor decides the list that applies to you:

• Primaquine, quinine and some other malaria medicines
• Sulfonamide (sulfa) medicines
• Quinolone antibiotics and nitrofurantoin
• Quinidine
• Large amounts of aspirin and non-steroidal anti-inflammatory painkillers
• Methylene blue and rasburicase, used in hospital

Pregnancy, children and special situations

Newborns: In babies with G6PD deficiency, jaundice is more common and sometimes severe. If G6PD deficiency runs in your family, tell the doctor who looks after your baby and have the jaundice watched closely.

Babies and young children are especially sensitive to mothballs. If mothballs are used, they should be kept in closed containers that do not let the vapor out and out of children’s reach.

Henna: Lawsone, the dye in henna, can cause red blood cell breakdown in people with G6PD deficiency. Most reported cases are in young babies and newborns; cases have also been reported from Türkiye. For this reason, it is advised not to apply henna to babies or to anyone with G6PD deficiency. Keep this in mind at ceremonies such as circumcision celebrations, weddings or henna nights.

Pregnancy: Some medicines can cross the placenta and cause breakdown in a baby who has G6PD deficiency. For every medicine you use during pregnancy, tell your doctor your G6PD status.

In Türkiye

In the Newborn Screening Program of the Turkish Ministry of Health (Sağlık Bakanlığı), the conditions screened with a heel-prick blood test are listed as phenylketonuria, congenital hypothyroidism, biotinidase deficiency, cystic fibrosis, congenital adrenal hyperplasia and spinal muscular atrophy. In the Ministry’s public education document for this program, G6PD deficiency is not among the screened conditions. So a normal heel-prick result does not mean there is no G6PD deficiency.

If there is G6PD deficiency or a history of jaundice after fava beans in your family, ask your doctor whether your baby and your other children need testing.

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