A 25-year-old woman of Mediterranean origin has a splenomegaly, mild chronic haemolytic anaemia, and peripheral smear showing target cells and basophilic stippling. Haemoglobin electrophoresis shows HbA2 6.5% (normal <3.5%) and HbF 3%. The diagnosis is beta-thalassaemia trait (minor). The elevated HbA2 is due to increased synthesis of which globin chain?

• A Gamma (γ) chains paired with alpha chains
• B Beta (β) chains in excess pairing with delta chains
• C Delta (δ) chains paired with alpha chains ✓
• D Epsilon (ε) chains retained from embryonic erythropoiesis

Explanation

HbA2 (α2δ2) is formed by alpha chains pairing with delta chains. In beta-thalassaemia, reduced beta-chain synthesis leads to relative excess alpha chains; delta-chain synthesis is upregulated to partially compensate, elevating HbA2 above 3.5%—the hallmark of beta-thalassaemia trait. Gamma chains compensate to form HbF (α2γ2).

Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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