Paget's disease of the bone is a metabolic bone disorder characterised by increased bone remodelling that results in abnormal bone production

Aetiology:

Not known - may be a genetic cause or triggered by a virus

Pathophysiology

In Paget's, the osteoclasts are multi-nucleated and increased in number and size. This results in an increase in bone resorption mediated by the osteoclasts. Osteoblasts respond by rapidly producing bone. Due to the rapidity of the bone turnover, the new bone produced is woven and therefore mechanically weak.

Paget's disease of the bone may be focal (a single lesion in the bone) or multifocal (multiple lesions in the skeleton). It has a predilection for the skull, spine, pelvis, femur and tibia.

Risk factors:

• increasing age
• male sex
• northern latitude
• family history

PC

Only 5% of patients are symptomatic

• the stereotypical presentation is an older male with bone pain and an isolated raised ALP
• bone pain (e.g. pelvis, lumbar spine, femur)
• classical, untreated features: bowing of tibia, bossing of skull

Investigations