A 65-year-old man with Paget's disease of bone presents with low back pain. Serum alkaline phosphatase is markedly elevated. X-ray of the pelvis shows a 'picture frame' appearance of the right ilium and cortical thickening. Which bone complication of Paget's disease carries the WORST prognosis?

• A Pathological fracture ('chalk stick' fracture of the femur)
• B Secondary osteoarthritis of the hip joint
• C Basilar invagination causing cranial nerve compression
• D Sarcomatous transformation (Paget's sarcoma) ✓

Explanation

Sarcomatous change (Paget's sarcoma) occurs in <1% of Paget's disease cases but carries a 5-year survival rate of less than 5%, making it by far the most lethal complication. It presents with sudden worsening of pain, new soft-tissue swelling, and a destructive lytic lesion on imaging. The histological type is usually osteosarcoma, fibrosarcoma, or MFH. Pathological fractures and OA are significant but treatable; basilar invagination can be severe but is manageable surgically.

Reference: Maheshwari Essential Orthopaedics, 6th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.