G6PD deficiency is a genetic condition involving a defect in the G6PD enzyme. It features episodes of haemolysis (red blood cell destruction) triggered by infections, medications or fava beans (broad beans).
It is X-linked recessive, meaning it usually affects males, as they only have a single copy of the gene on their single X chromosome. It is more common in people of Mediterranean, Middle Eastern and African descent.
TOM TIP: The typical exam patient with G6PD deficiency becomes jaundiced and anaemic after eating broad beans, developing an infection or being treated with antimalarial medications.
Pathophysiology
Red blood cells are constantly exposed to oxidative stress from normal metabolism, infections, and certain drugs or foods. The G6PD enzyme helps protect red blood cells from oxidative damage.
G6PD helps produce NADPH (nicotinamide adenine dinucleotide phosphate), which keeps glutathione in its reduced and active form. Reduced glutathione neutralises oxidative molecules.
G6PD deficiency leaves red blood cells more vulnerable to oxidative damage during periods of increased stress, leading to damaged haemoglobin (forming Heinz bodies) and haemolysis (red blood cell destruction).
Presentation
G6PD deficiency often presents with neonatal jaundice, which can be severe, risking kernicterus (brain damage).
Other features of the condition include:
- Anaemia
- Intermittent jaundice, particularly in response to triggers
- Gallstones
A blood film can show:
- Heinz bodies (blobs of denatured haemoglobin (“inclusions”) seen within RBCs)
- Bite cells (RBCs with a “punched out” section where macrophages in the spleen have removed Heinz bodies)
Diagnosis can be made by doing a G6PD enzyme assay. This can be falsely normal during acute haemolysis, as enzyme-deficient cells have been destroyed, leaving behind only younger cells with higher enzyme levels.
Management
Patients should avoid triggers of acute haemolysis, such as fava beans and certain medications, such as:
- Primaquine (an antimalarial)
- Nitrofurantoin
- Co-trimoxazole
- Sulfasalazine
Last updated April 2026
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