A 35-year-old woman of Mediterranean origin is found to have haemoglobin 9.2 g/dL, MCV 62 fL, low MCH, target cells, and HbA2 4.8% on HPLC. Serum ferritin is 18 ng/mL. Which is the correct interpretation?
- A Beta-thalassaemia major
- B Sickle cell trait
- C Beta-thalassaemia trait with co-existing iron deficiency ✓
- D Alpha-thalassaemia trait
Correct answer: C. Beta-thalassaemia trait with co-existing iron deficiency
Explanation
HbA2 > 3.5% (here 4.8%) on HPLC is diagnostic of beta-thalassaemia trait. Co-existing iron deficiency can lower HbA2 towards normal, potentially masking the diagnosis; this patient's low ferritin indicates iron deficiency coexisting with beta-thal trait. After iron repletion, HbA2 would be expected to rise further. Beta-thal major would present with transfusion-dependent severe anaemia from infancy. Sickle cell trait would show HbA and HbS bands. Alpha-thalassaemia trait has normal HbA2.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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