A 19-year-old man develops dark urine, jaundice, and abdominal pain two days after eating fava beans. Smear shows bite cells and Heinz body-positive cells. He is treated supportively. If G6PD enzyme assay is sent now, the result may be falsely reassuring because:
- A Younger red cells and reticulocytes have higher residual G6PD activity than the lysed older population ✓
- B Fava bean metabolites directly inhibit the assay reagent
- C Heinz bodies absorb the spectrophotometric signal used in the assay
- D Complement-mediated lysis removes all enzyme-deficient cells before sampling
Correct answer: A. Younger red cells and reticulocytes have higher residual G6PD activity than the lysed older population
Explanation
During the acute episode the most severely deficient erythrocytes have been destroyed, leaving behind younger cells and reticulocytes that retain relatively higher G6PD levels, so the assay can be falsely near-normal. Definitive testing should be repeated several weeks after recovery. G6PD deficiency is X-linked, affects males predominantly, and classically follows exposure to oxidant drugs, fava beans, or infection.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.