In Paget's disease of bone, the pelvis is the most commonly affected bone. A 68-year-old man with known Paget's disease presents with new onset rapidly worsening hip and thigh pain. X-ray shows a lytic 'flame-shaped' lesion within the pagetic femur with cortical destruction. Serum alkaline phosphatase is markedly elevated (baseline 850 IU/L, now 2200 IU/L). What complication must be immediately suspected and how is it confirmed?
- A Pathological fracture of the pagetic femur — confirm with CT scan
- B Pagetic crisis from hypercalcemia — confirm with serum calcium
- C Secondary hyperparathyroidism — confirm with serum PTH
- D Sarcomatous transformation (Paget's sarcoma) — confirm with MRI and biopsy ✓
Explanation
Sarcomatous transformation (most commonly osteosarcoma, rarely fibrosarcoma or chondrosarcoma) is the most feared complication of Paget's disease, occurring in <1% of monostotic and ~5-10% of polystotic disease. Hallmarks: rapidly worsening pain in a known pagetic site, new lytic destructive lesion on X-ray with cortical break, and a dramatic rise in serum ALP above the pagetic baseline. MRI shows cortical destruction and soft tissue mass; biopsy confirms sarcoma. Prognosis is extremely poor (median survival 8 months). A 'flame-shaped' lucent front within pagetic bone is the characteristic advancing lytic front of Paget's, but new cortical destruction superimposed on this with rising ALP signals malignant transformation.
Reference: Maheshwari Essential Orthopaedics, 6th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.