Paget Disease

Basics

Paget disease involves resorption of normal bone and its replacement with fibrous and sclerotic tissue
Also known as osteitis deformans
Usually focal, bones most frequently involved include:
- Pelvis
- Femur
- Skull
- Tibia
- Spine
- Flat bones
Usually found incidentally and generally asymptomatic
Occurs in ∼1–2% of patients >55 yr old
Incidence increases with age
Starts with resorptive or osteolytic phase, during which osteoclasts remove healthy bone
Hypervascularity begins in resorptive phase:
- Predisposes to hematoma and fracture
Resorbed bone is eventually replaced by irregular, dense, disorganized trabecular bone in sclerotic or osteoplastic phase forming “mosaic pattern”
Malignant transformation is rare:
- Osteosarcoma is malignancy of concern
- Usually malignant transformation occurs in 1%
More common in men
More common in European descent
Less common in Asian or Scandinavian descent
Typically involves 1 bone (monostotic)
May involve a few bones (polyostotic)

Unknown
Genetic component:
- SQSTM1 mutation seen in many but not all cases
- Patients with this mutation may present at a younger age
- Paget disease may have genetically linked mutations seen in multisystem proteinopathies such as ALS and frontotemporal dementia
Environmental influences may also play a role:
- Presence of nucleocapsids from measles, canine distemper, paramyxovirus, or respiratory syncytial virus may implicate viral cause
- Possible association with rural life and close contact with farm animals
May represent vascular hyperplasia with subsequent inflammation
Increased nucleoli and intranuclear inclusion bodies seen in osteoclasts on microscopy

Pediatric Considerations
Generally not seen in children

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