A healthy 26-year-old man donating blood for a family member is found to have hemoglobin 11.2 g/dL, MCV 63 fL, RDW 12%, and normal serum ferritin. Hemoglobin electrophoresis shows HbA2 6.2% and HbF 2%. What is the most likely diagnosis?

• A Iron deficiency anemia
• B Beta-thalassemia trait (minor) ✓
• C Anemia of chronic disease
• D Sideroblastic anemia

Explanation

Beta-thalassemia minor shows microcytosis disproportionately severe relative to mild or absent anemia, a low Mentzer index (MCV/RBC below 13), normal iron studies, and a diagnostic rise in HbA2 above roughly 3.5 percent due to reduced competition from absent beta chains allowing excess delta chain pairing. Normal ferritin excludes iron deficiency, option A, the commonest misdiagnosis. Sideroblastic anemia requires marrow ring sideroblasts, and chronic disease raises ferritin with low iron binding capacity.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

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