Paget Disease

KEY FACTS

Terminology

• Chronic metabolic skeletal disorder

• Characterized by bony expansion with variable destruction ± sclerosis

Imaging

• Well-circumscribed, sharply marginated defects &/or marked thickening + sclerosis

• Skull in 25-65% (may be isolated to skull base)

  • Diploic widening, coarse trabecula, thick cortices

  • “Tam-o'-shanter” skull: Marked ↑ diploic space, particularly inner table

  • “Cotton wool” skull: Focal sclerosis within previous areas of “osteoporosis circumscripta”

• Platybasia

• Typically “hot” throughout all bone scan acquisitions (blood flow, blood pool, static)

• Bone scans + radiographs abnormal in 56-86%

Top Differential Diagnoses

• Osteosclerotic metastases

• Osteolytic metastases

• Fibrous dysplasia

• Other causes of calvarial thickening

Pathology

• Excessive and abnormal remodeling of bone, with both active and quiescent phases

  • Localized areas of ↑ bone resorption + exuberant but aberrant new bone formation

• Individual sites progress at variable rates

  • PD of differing phases may be seen within same patient

Clinical Issues

• 20% asymptomatic; pain, tenderness, ↑ hat size

• New pain/swelling → malignant transformation

TERMINOLOGY