What is the recommended evaluation and management for Paget's disease of the pelvis in an adult patient over 50 years old?

Paget's Disease of the Pelvis: Evaluation and Management

Diagnostic Approach

For adults over 50 with suspected Paget's disease of the pelvis, obtain plain radiographs first, followed by total serum alkaline phosphatase measurement with liver function tests, and then perform bone scintigraphy to map the full extent of skeletal involvement. 1

Initial Imaging

• Plain radiographs of the pelvis are the first-line investigation, showing the characteristic mixed osteolytic and osteosclerotic appearance that defines Paget's disease 1, 2
• The pelvis is one of the most commonly affected sites (30-75% of cases), making it a typical presentation location 2
• Radiographic features progress through three phases: initial osteolysis, followed by mixed lytic-sclerotic changes with trabecular thickening and bone enlargement, and finally predominant sclerosis 2

Biochemical Testing

• Measure total serum alkaline phosphatase as the primary screening test, combined with liver function tests to exclude hepatic causes of elevation 1
• More specific bone turnover markers (PINP or CTX) can be used when alkaline phosphatase results are equivocal 1
• Elevated alkaline phosphatase is a key diagnostic feature, though the disease may be discovered incidentally even with normal levels 3, 4

Extent Mapping

• Perform bone scintigraphy with radionuclides once diagnosis is confirmed to determine the full extent of skeletal involvement 1
• Bone scans demonstrate marked increased uptake in all phases of Paget's disease and reveal clinically silent lesions that would otherwise go undetected 2

Differential Diagnosis Considerations

Key distinguishing features of Paget's disease include 3:

• Family history of Paget's disease
• Pelvic or skull localization
• Raised alkaline phosphatase
• Bone deformities on examination
• Characteristically mixed osteolytic and osteosclerotic appearance on imaging
• Age of onset usually >50 years (critical distinguishing feature)

Must exclude malignancy, particularly osteosarcoma, which can develop as a secondary malignancy in elderly patients with Paget's disease 3

Treatment Recommendations

Zoledronic acid 5 mg as a single intravenous infusion is the treatment of choice for patients with active Paget's disease who are at risk of future complications and have no contraindications. 1, 5

Indications for Treatment

Treat patients with 1, 5, 4:

• Symptomatic disease (bone pain is the most common symptom)
• Active disease at sites where complications are likely (pelvis qualifies as high-risk site)
• Risk of nerve compression, fracture, or progressive deformity
• Pagetic arthritis affecting adjacent joints

Critical caveat: Bisphosphonates should be reserved for symptomatic patients or those at high risk of complications, as treatment of asymptomatic disease has been associated with increased fracture rates 5

Specific Bisphosphonate Regimens

First-line option:

• Zoledronic acid 5 mg as single IV infusion over at least 15 minutes leads to sustained reduction in bone pain and bone turnover markers for months 1, 5, 6

Alternative regimens (particularly relevant for renal impairment):

• Pamidronate 30 mg IV daily over 4 hours for 3 consecutive days (total 90 mg) has sustained effects for months 1, 7
• Risedronate is effective but contraindicated if GFR <30 mL/min/1.73 m² 7, 3
• Alendronate not recommended if GFR <35 mL/min/1.73 m² 7, 3

Pre-Treatment Requirements

Before administering bisphosphonates, you must: 1, 6

• Ensure adequate calcium and vitamin D levels to prevent hypocalcemia
• Measure serum creatinine and calculate actual creatinine clearance (use Cockcroft-Gault, not estimated GFR alone) 6
• Correct any vitamin D deficiency before treatment 6

Monitoring Treatment Response

• Measure total serum alkaline phosphatase at 3-6 months to evaluate initial treatment response 4
• Monitor serum creatinine, calcium, phosphate, and magnesium before any repeat infusions 6
• Discontinue if unexplained creatinine increase >0.5 mg/dL or absolute value >1.4 mg/dL occurs 6

Complications Requiring Surgical Consultation

Orthopedic complications that may require surgical intervention include 8:

• Pathologic fractures with delayed union
• Progressive skeletal deformity causing functional impairment
• End-stage pagetic arthritis of the hip (total hip replacement)
• Spinal stenosis with neurologic symptoms (decompressive laminectomy)

Sarcomatous transformation occurs in approximately 1% of cases and appears on imaging as focal bone destruction extending through cortex with soft-tissue mass—this is the most feared complication requiring immediate oncologic referral 2, 3