G6PD deficiency
Description
- The commonest enzymopathy in the world - ~400 million people
- X-linked recessive - males hemizygous and affected; females heterozygous with a variable phenotype from lyonisation
- Episodic acute haemolysis triggered by oxidative stress, on a background of normal blood counts
- Between episodes the FBE, LDH and film are entirely normal - this is the diagnostic pitfall
Clinical variants (WHO classification)
| Class | Activity | Phenotype |
|---|---|---|
| I | <1% | Chronic non-spherocytic haemolytic anaemia (rare, sporadic mutations) |
| II | <10% | Mediterranean, Asian - severe episodic haemolysis, favism |
| III | 10-60% | African (A-) - milder, self-limiting episodes |
| IV | Normal | Non-deficient variant |
- *African A- variant is self-limiting because the enzyme is unstable rather than absent* - young red cells retain enough activity, so haemolysis stops even with continued exposure
- *Mediterranean variant does not self-limit* - haemolysis continues while the trigger persists
6 more sections, plus exam facts
Premium unlocks every note across every specialty, and the full exam fact library behind it.
Get premium access