Bone marrow examination of a patient with refractory anemia shows erythroid hyperplasia with normoblasts containing numerous iron granules arranged as a complete ring around the nucleus. The iron in these cells is deposited primarily in which organelle?

• A Lysosomes
• B Nucleus itself
• C Endoplasmic reticulum
• D Mitochondria ✓

Explanation

Ring sideroblasts contain iron accumulated within mitochondria of erythroid precursors. Defective heme synthesis, classically impairment of the final step catalyzed by ferrochelatase or reduced ALAS2 activity, prevents incorporation of iron into protoporphyrin, so non-heme iron piles up in mitochondria, which cluster around the nucleus. Lysosomal iron appears as ordinary siderotic granules or Pappenheimer bodies in mature red cells, not as a perinuclear ring. More than 15 percent ringed sideroblasts defines sideroblastic anemia.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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