In beta-thalassemia major, ineffective erythropoiesis leads to massive extramedullary hematopoiesis. The characteristic 'hair-on-end' appearance on skull X-ray is due to:
- A Reactive widening of the diploic space due to marrow hyperplasia ✓
- B Subperiosteal hemorrhage in the diploic space
- C Lytic bone lesions from extramedullary hematopoietic tissue
- D Calcium deposits in the subdural space
Correct answer: A. Reactive widening of the diploic space due to marrow hyperplasia
Explanation
In beta-thalassemia major, severe ineffective erythropoiesis causes massive compensatory bone marrow expansion that widens the diploic space of the skull, thinning the outer table and producing perpendicular bone spicules visible on X-ray as the 'hair-on-end' pattern. Similar changes occur in sickle cell disease. This is not due to hemorrhage, lytic lesions, or calcification.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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