A 22-year-old woman has a haemolytic anaemia with negative Coombs test. Peripheral smear shows 'bite cells' and 'blister cells'. Heinz body preparation is positive. G6PD level is normal (measured during an acute haemolytic episode). Which is the MOST likely explanation for the normal G6PD level?
- A G6PD-deficient reticulocytes have higher G6PD activity, falsely normalising results during haemolysis ✓
- B The diagnosis is hereditary spherocytosis, not G6PD deficiency
- C G6PD A- variant does not cause haemolysis in females
- D Heinz bodies are specific to drug-induced thrombocytopenia, not G6PD deficiency
Explanation
In G6PD deficiency, acute haemolytic episodes preferentially destroy older red cells with the lowest G6PD activity. The surviving population after haemolysis is enriched with younger red cells and reticulocytes, which normally have higher G6PD enzyme activity. This can falsely normalise G6PD levels measured during or shortly after an acute haemolytic episode. Testing should be repeated 2–3 months after recovery when the red cell population has normalised. Bite cells and Heinz bodies (oxidised denatured haemoglobin) are characteristic of G6PD deficiency; Heinz bodies are not seen in HS.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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Written and medically reviewed by the StethoPrep medical team.