A 68-year-old man has bone pain in the pelvis and skull. Serum alkaline phosphatase is markedly elevated while calcium and phosphate are normal. Skull X-ray shows thickening of the calvarium with mixed lytic and sclerotic areas. Biopsy shows cement lines arranged in a haphazard mosaic pattern with numerous multinucleated osteoclasts. What is the diagnosis?
- A Paget disease of bone ✓
- B Fibrous dysplasia
- C Osteomalacia
- D Renal osteodystrophy
Correct answer: A. Paget disease of bone
Explanation
The mosaic pattern of lamellar bone joined by irregular cement lines is pathognomonic of Paget disease, driven by abnormal osteoclast activity. Alkaline phosphatase is high while serum calcium and phosphate remain normal. In fibrous dysplasia the normal marrow is replaced by fibrous tissue without osteoblastic rimming and no mosaic cement lines form, which excludes that distractor.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.