Anemias USMLE Step 1 Practice Question
A 47-year-old man is evaluated for fatigue and numbness in his feet. He has alcohol use disorder and recently began isoniazid for latent tuberculosis. Laboratory studies show hemoglobin 9.8 g/dL and MCV 74 fL. Iron studies reveal high ferritin and high serum iron with normal total iron-binding capacity. Bone marrow aspirate demonstrates erythroid precursors with iron-laden mitochondria arranged in a ring around the nucleus. Which of the following is the most likely underlying defect?
Answer choices
- AAbsence of the PIGA gene in hematopoietic stem cells
- BImpaired protoporphyrin synthesis due to reduced pyridoxine-dependent ALA synthase activityCorrect answer
- CReduced globin chain synthesis from beta-globin mutation
- DDecreased hepcidin synthesis
- EAutoimmune destruction of gastric parietal cells
- FImpaired iron transport due to defective transferrin receptor expression
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