A 70-year-old man has Paget's disease affecting the proximal tibia. Serum calcium, phosphate, and PTH are normal. Serum alkaline phosphatase (ALP) is markedly elevated at 850 IU/L. He develops progressive leg bowing. Which complication carries the highest mortality risk in advanced Paget's disease?

• A Pathological fracture through pagetic bone
• B High-output cardiac failure from extensive AV shunting in hypervascular pagetic bone
• C Sarcomatous transformation (Paget's sarcoma) — osteosarcoma arising in pagetic bone ✓
• D Basilar invagination with hydrocephalus

Explanation

Sarcomatous transformation (most commonly osteosarcoma, less often fibrosarcoma or chondrosarcoma) occurs in approximately 1% of patients with polyostotic Paget's disease and carries an extremely poor prognosis with 5-year survival below 5%. It typically presents as sudden increase in pain, rapid expansion of affected bone, and markedly elevated ALP. High-output cardiac failure can occur in extensive Paget's but is manageable. Pathological fractures occur but heal. Basilar invagination is a less common neurological complication.

Reference: Maheshwari Essential Orthopaedics, 6th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.