A screening programme measures zinc protoporphyrin in whole blood. Besides lead poisoning, which condition will most likely produce an elevated value?

• A Hereditary spherocytosis
• B Vitamin B12 deficiency anaemia
• C Iron deficiency anaemia ✓
• D Beta thalassaemia minor

Explanation

When iron supply is insufficient, whether from lead blocking iron delivery or from simple iron deficiency, ferrochelatase inserts zinc instead of iron into protoporphyrin IX, raising blood zinc protoporphyrin. This is why zinc protoporphyrin alone cannot distinguish lead toxicity from iron deficiency. Vitamin B12 deficiency and thalassaemia minor affect DNA synthesis or globin production respectively, while hereditary spherocytosis is a membrane defect, none of which limit iron availability at the ferrochelatase step.

Reference: Harper's Illustrated Biochemistry, 32nd ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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