Glucose 6 Phosphate Dehydrogenase (G6PD) Deficiency

G6PD is short for, Glucose 6 Phosphate Dehydrogenase, which is a substance found in red blood cells and helps prevent chemicals from damaging the red blood cells. Some people have a deficiency of this substance and are said to be G6PD deficient. In other words they have a reduced amount of G6PD in their blood. Sometimes this deficiency can cause health problems.

Populations affected

G6PD deficiency is most commonly seen in people whose ancestors originate from areas of the world where malaria is or was common, for example, the Mediterranean, Africa, Middle and Far East and Asia.

Approximately:

  • 1 in every 12 Greek Cypriots are G6PD deficient,
  • 1 in every 5 Africans are G6PD deficient,
  • 1 in every 10 African-Caribbean are G6PD deficient,
  • 1 in every 5 Indians are G6PD deficient,
  • 1 in every 30 Chinese,
  • 1 in every 5 Thais are G6PD deficient.

It has been suggested that G6PD deficiency offers some protection against malaria.

Types of G6PD Deficiency

There are different types of G6PD deficiency and these tend to affect specific ethnic groups. The type seen in the South East Asian and Mediterranean population is often the most severe form, whilst the type seen in Black people is often milder.

Inheritance of G6PD Deficiency

G6PD deficiency is a genetically inherited condition and the gene for G6PD can be found on the female sex (X) chromosome.

Women have two X chromosomes (XX), one from each parent, whilst men only have only one which they get from their mother and a male Y chromosome from their father (XY). Because men only have one X chromosome G6PD affects more men than women. If a man inherits G6PD deficiency on his one X chromosome which he gets from his mother he will be G6PD deficient.

A woman inherits two X chromosomes, one from each parent; therefore, if she inherits one normal X chromosome and one G6PD deficient X chromosome she will be an unaffected carrier because she still has one normal X chromosome. However, if she inherits two G6PD deficient X chromosomes she will be affected.

Examples of G6PD inheritance patterns

(X = normal      Xg = G6PD deficient)

Example 1: If a woman carries the G6PD deficiency gene and the man does not, here are the chances for their offspring:

Woman

X Xg
Male

X Y
CHILD
 
X X
Normal
Female
X Y
Normal
Male
Xg X
Unaffected
(Carrier) Female
Xg Y
Affected
Male

Example 2: a woman is not a carrier of the G6PD deficiency gene and the man is affected:

Woman

X X
Male

Xg Y
CHILD
 
X Xg
Unaffected
(Carrier) Female
X Y
Unaffected
Male
X Xg
Unaffected
(Carrier) Female
X Y
Unaffected
Male

Example 3: If a woman is an unaffected carrier of the G6PD deficiency gene and the man is affected:

Woman

Xg X
Male

Xg Y
CHILD
 
Xg Xg
Affected
Female
Xg Y
Affected
Male
X Xg
Unaffected
(Carrier) Female
X Y
Unaffected
Male

Effects of G6PD Deficiency

Most people with G6PD deficiency live normal lives and are healthy. It is only when certain things trigger a reaction in the red blood cells that the G6PD deficiency becomes a problem. This may occur when a person has an infection, fever, or when they take into their body a substance or chemical which the G6PD deficient red blood cell cannot cope with. When this occurs the red blood cells will react and get broken down and destroyed prematurely, the individual becomes anaemic (pale blood) and jaundiced (yellowness especially of the white of the eye). But, once the trigger factor is removed, the individual’s health will return to normal.

Management of G6PD Deficiency

Problems can be avoided if a person gets to know which type of G6PD deficiency they have inherited and obtain a list of the specific chemicals and drugs which may trigger a reaction in their red blood cells. Irrespective of the type of G6PD the individual has inherited they must avoid getting infections but if they do become unwell to seek treatment promptly.

Only a few drugs and chemicals are certain to cause anaemia and jaundice. Different types of G6PD deficiency react to drugs and chemicals differently and not all of them will cause a reaction in everyone with G6PD.

The most common chemicals and drugs include some forms of:

Antibiotics eg. Sulphanamides, Chloramphenicol
Pain relievers eg. Paracetamol, Aspirin
Malaria Drugs eg. Primaquine, Pentaquine
Other Substances eg. Moth Balls, Fava (Broad) Beans including its pollen

This list is not an exhaustive list, if a person has been diagnosed as G6PD deficient they will need to be told the type of G6PD deficiency they have inherited and given a complete list of the drugs and chemicals that they need to avoid.

It may be necessary to give someone with G6PD one of the drugs listed if it is the best medication for treating their ailment, in which case the doctor may suggest monitoring the individual’s blood regularly whilst you are taking the drug to check that the drug is not causing a reaction and if it is the doctor may limit how long the person should use the drug for or suggest giving other medications to correct the anaemia.

Newborn Babies with G6PD Deficiency

If a new born baby has inherited G6PD deficiency the baby may become jaundiced soon after birth and need treatment under a special light called a ‘photo therapy’ lamp.

Once the jaundice is corrected and the other trigger factors are avoided the child should remain well generally and the G6PD deficiency need not be a problem.

Testing for G6PD Deficiency

People can request further information or testing for G6PD deficiency by discussing it with their GP or contacting one of the National Sickle Cell / Thalassaemia Centres. They should also ask about Sickle Cell and Thalassaemia, see Haemoglobin, because these conditions affect similar populations, for example, a person may inherit sickle cell trait as well as be G6PD deficient. Testing for these conditions can be done at the same time.