Glucose-6-phosphate dehydrogenase deficiency (G6PDD) Dr Trisha Macnair G6PDD is a common inherited condition that occurs when the body lacks an important enzyme called glucose-6-phosphate dehydrogenase (G6PD).

In this article

What causes it? What are the symptoms?

Who's affected? How is it diagnosed?

How's it treated?

G6PDD is caused by a fault in a gene found on the X chromosome.

The enzyme G6PD protects against oxidation and red blood cells are particularly reliant on this enzyme.

When levels of G6PD are low, the red blood cells break down, or haemolyse, when exposed to certain triggers. This leads to anaemia and a reduction in the amount of oxygen carried around the body.

Common triggers for G6PDD include:

• Infections - bacterial or viral
• Ingestion of broad (fava) beans (which is why it's also called favism)
• Certain types of drugs - including aspirin, non-steroidal anti-inflammatory drugs (NSAIDs, such as ibuprofen), certain antibiotics (such as sulphonamide, nitrofurantoin), dapsone (an antileprotic), glibenclamide (an antidiabetic) and antimalarial drugs (such as primaquine and quinine)

The G6PD Deficiency Association provides a comprehensive list of triggers.

More than 400 variants of G6PDD have been identified, and their severity varies greatly depending on the form.

Within two to three days of being exposed to a trigger, a person with G6PDD may develop breakdown of their red blood cells, known as haemolysis. This can cause fever and anaemia, with symptoms of paleness, shortness of breath, a fast, weak pulse and tiredness.

Jaundice (a yellow colouring of the skin) may also develop, and there may be dark orange or red discoloration of the urine (due to blood or its pigments).

The episodes are usually short-lived because the body reacts to blood-cell breakdown by producing new (young) red blood cells, which have normal G6PD activity. But if the anaemia is severe, there's a risk of kidney failure or even death, and the person may need a blood transfusion.

Some people with certain forms of the condition may experience a chronic breakdown of the blood cells. In one form, newborn babies are particularly vulnerable.

If there's chronic haemolysis, a course of folic acid supplements may be needed.

More than 400 million people around the world are affected by G6PDD, and it's particularly common in people of Mediterranean and African descent. It's also more common in south-east Asia.

As men only carry one copy of the X chromosome, they're more likely than women to have G6PDD, and are usually more severely affected.

G6PDD can be detected easily with a blood test, and in many countries there's screening for the condition.

The most important aspect of treatment is preventing anaemia by understanding and avoiding trigger factors, and treating events such as infection quickly and effectively.

This article was last medically reviewed by Dr Rob Hicks in April 2008