A 68-year-old man with known Paget's disease of the skull presents with headaches and increasing hat size. Skull X-ray shows well-defined areas of rarefaction in the frontal and parietal bones with patchy sclerosis giving a 'cotton wool' appearance. This radiological finding is characteristic of which stage of Paget's disease?

• A Lytic (hot) stage
• B Pre-vascular quiescent stage
• C Sclerotic (cold) stage
• D Mixed (lytic and blastic) stage ✓

Explanation

The 'cotton wool' appearance in the skull results from patchy areas of bone resorption (rarefaction) intermixed with irregular new bone formation (sclerosis), characteristic of the mixed osteolytic and osteoblastic stage. The purely lytic stage shows osteoporosis circumscripta as well-defined radiolucent areas without sclerosis. The cold stage shows predominant sclerosis.

Reference: Bailey and Love's Short Practice of Surgery, 28th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.