Paget's Bone Disease

Definition

Paget's bone disease (osteitis deformans) is a chronic disorder of bone remodeling, characterized by excessive bone resorption followed by disorganized and excessive bone formation, resulting in structurally weak and deformed bones.

Epidemiology

• More common in individuals over 50 years of age
• Slight male predominance
• Prevalence varies geographically; highest in Western Europe, North America, Australia
• Rare in Asia and Africa
• Often asymptomatic and incidentally diagnosed

Etiology

• Exact cause unknown; likely multifactorial (genetic susceptibility and environmental factors)
• Mutations in SQSTM1 gene associated with familial cases
• Viral etiology (paramyxovirus) has been hypothesized but not confirmed
• Environmental factors may influence disease expression

Pathophysiology

• Increased osteoclastic bone resorption → increased osteoblastic activity → disorganized woven bone
• Affected bone is enlarged, deformed, hypervascular, and weaker than normal bone
• Altered remodeling leads to increased bone turnover markers (alkaline phosphatase)
• Mechanical weakness predisposes to fractures, deformities, and osteoarthritis