Conditions · Metabolism: carbohydrates and glycogen
Glucose-6-phosphate dehydrogenase (G6PD) deficiency !
With G6PD deficiency red blood cells break down after certain drugs, fava beans or infections; most people have no symptoms between episodes.
Updated 2026-11-01
Structures involved
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In biochemistry
- Pentose phosphate pathway: Step 1 · Glucose-6-phosphate dehydrogenase (G6PD)
- Glucose-6-phosphate dehydrogenase (G6PD)
- NADPH
- Lactate dehydrogenase (LDH) as a lab marker
In the clinical exam
In physiology
- Anemia physiology and compensation
- The red cell life cycle and the spleen
- Carbon monoxide, methemoglobin and cyanide
Why it happens
- Oxidative stress and free-radical injury
- Mendelian inheritance: autosomal dominant, recessive and X-linked
What it is
Inherited X-linked enzyme defect in which the red cell has little G6PD and cannot make the NADPH that protects it from oxidants.
Who gets it
About 400 million people worldwide; common in Africa, Asia, the Mediterranean and the Middle East. In Colombia it is commoner in Afro-descendant populations and in the malarial Pacific and Caribbean regions.
Causes
- G6PD gene variants on the X chromosome (X-linked recessive inheritance)
Risk factors
- Male sex
- African, Mediterranean, Asian or Middle Eastern ancestry
- Family history of haemolytic anaemia or neonatal jaundice
Pathophysiology
G6PD is the first step of the pentose pathway and the red cell's only source of NADPH. Without NADPH reduced glutathione is not regenerated and hydrogen peroxide oxidises haemoglobin, which precipitates as Heinz bodies; the spleen «bites» out these inclusions (bite cells) and destroys the cells. Fava beans, oxidant drugs (primaquine, tafenoquine, dapsone, rasburicase, nitrofurantoin, some sulfonamides), naphthalene and infections trigger acute, mainly intravascular haemolysis.
Classification
- Variants with severe deficiency and chronic haemolytic anaemia (rare)
- Variants with moderate to severe deficiency and haemolysis only with triggers (most; e.g. African A− and Mediterranean)
Symptoms and signs
- Neonatal jaundice
- Pallor, fatigue and fast heartbeat during a crisis
- Dark urine (haemoglobinuria) 1–3 days after the trigger
- Back or abdominal pain and fever during haemolysis
Diagnosis
- Clinical
- Acute haemolysis a few days after fava beans, an oxidant drug or an infection, in someone well before the episode.
- Tests
- Low haemoglobin, high reticulocytes, indirect bilirubin and LDH, low haptoglobin; smear with Heinz bodies and bite cells. Low G6PD activity (qualitative or quantitative test); during a crisis it can be falsely normal because of reticulocytes and is repeated weeks later.
- Imaging
- Imaging is not needed for diagnosis; abdominal ultrasound may show gallstones or a large spleen.
Treatment
- Lifestyle
- Avoid fava beans, naphthalene and oxidant drugs; carry a list of medicines to avoid
- Acute
- Stop the trigger, hydrate, and transfuse red cells in severe haemolysis
- Medical
- Phototherapy or exchange transfusion in severe neonatal jaundice
- Follow-up
- G6PD testing before primaquine, tafenoquine, dapsone or rasburicase
Complications
- Severe acute haemolytic anaemia
- Acute kidney injury from haemoglobinuria
- Kernicterus in the newborn
- Pigment gallstones
Prognosis
Most live symptom-free if they avoid triggers; crises usually resolve within weeks.
Prevention
- Newborn screening where available and G6PD testing before high-risk drugs
Test yourself
Think of the answer, then tap the question to see it.
Which inclusions are seen on the smear during a G6PD-deficiency crisis?
Heinz bodies (oxidised haemoglobin) and bite cells.
Why can G6PD activity be normal during a crisis?
The oldest cells have already been destroyed and young reticulocytes have more enzyme.
Which food is the classic trigger of favism?
Fava beans (Vicia faba).
Why is G6PD deficiency commoner in malarial areas?
Carriers and affected people have some protection against severe P. falciparum malaria.
Related conditions
Educational information, not medical advice. For any symptom, see a health professional.
Sources: Glucose-6-phosphate dehydrogenase deficiency: MedlinePlus Genetics (MedlinePlus, US National Library of Medicine, 2026); Glucose-6-phosphate dehydrogenase deficiency: MedlinePlus Medical Encyclopedia (MedlinePlus, US National Library of Medicine, 2026); G6PD gene: MedlinePlus Genetics (MedlinePlus, US National Library of Medicine, 2026); Textbook of Biochemistry for Medical Students, 6th ed. (Jaypee Brothers Medical Publishers (Vasudevan DM, Sreekumari S, Vaidyanathan K), 2011).
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