Bone marrow aspirate from a 66-year-old man with unexplained anemia is stained with Prussian blue. Several normoblasts show blue granules arranged in a full circle around the nucleus. These ringed sideroblasts indicate pathological accumulation of iron in which cellular compartment?

• A Lysosomes of reticuloendothelial macrophages
• B Cytosolic ferritin aggregates of plasma cells
• C Mitochondria of erythroid precursors ✓
• D Nucleus of orthochromatic normoblasts

Explanation

Sideroblastic anemia results from defective heme synthesis within the erythroid precursor. Iron delivered to the mitochondrion cannot be incorporated into protoporphyrin by ferrochelatase, so it accumulates in mitochondrial iron deposits. On Prussian blue stain these encircle the nucleus, forming ringed sideroblasts. Normal siderosomes are cytoplasmic, and iron loading of reticuloendothelial macrophages is the pattern of anemia of chronic disease, not of ringed sideroblast formation.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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