Courtesy: OI Foundation
Paget Disease of Bone (Osteitis Deformans)
Overview
Paget disease of bone is a chronic disorder of bone remodeling, first described by Sir James Paget in 1876.
- Characterized by:
- Excessive osteoclastic bone resorption
- Followed by disorganized osteoblastic bone formation
Result
- Enlarged bone
- Structural weakness
- Bone deformities
Epidemiology
Prevalence
- Previously:
- 3–4% of individuals >50 years
- Now:
- Significantly reduced in many regions
Demographics
- Affects men and women equally
- Less common in:
- Asian populations
- Scandinavian populations
Genetic Pattern
- Familial cases: 20–30%
Extent of Disease
- Monostotic (single bone)
- Polyostotic (multiple bones)
- Entire skeleton involvement is rare
Clinical Presentation
Symptoms
- Often asymptomatic
- Frequently diagnosed incidentally
Common Features
- Persistent bone pain
- Bone enlargement:
- Skull
- Long bones
Incidental Diagnosis
- X-rays taken for other reasons
- Elevated alkaline phosphatase on routine testing
Bone Deformities
Common Deformities
- Bowing of tibia
- Skull enlargement
Consequences
- Secondary osteoarthritis
- Altered biomechanics
Complications
Skeletal Complications
- Pathological fractures
- Bone deformity
- Secondary osteoarthritis
Neurological Complications
- Nerve root compression
- Spinal cord compression
- Posterior fossa compression
Auditory Complications
- Hearing loss (skull involvement)
Metabolic Complications
- Hyperuricemia
- Gout
- Hypercalcemia (especially with immobilization)
Cardiovascular Complications
- High-output cardiac failure due to increased bone vascularity
Rare Complications
- Osteosarcoma
- Giant cell tumor
Stages of Disease
1. Osteolytic Phase
- Increased osteoclastic activity
- Radiology:
- Osteolytic lesions
- Often asymptomatic
2. Mixed Phase
- Both resorption and formation
- Bone becomes:
- Enlarged
- Structurally abnormal
3. Sclerotic Phase
- Dense, thick bone formation
- Leads to:
- Deformity
- Complications (e.g., hearing loss)
Medical Treatment
Calcitonin
- Older treatment option
- Administered as injections
Advantages
- Pain relief within 2–4 weeks
Limitations
- Requires injections
- Side effects:
- Nausea
- Less effective than newer drugs
Bisphosphonates (First-Line Treatment)
Common Drugs
- Etidronate
- Pamidronate
- Alendronate
- Risedronate
- Zoledronic acid
Mechanism
- Inhibit osteoclast-mediated bone resorption
Most Effective Drug
- Zoledronic acid:
- Single IV dose (5 mg)
- Normalizes alkaline phosphatase
- Effect lasts ?5 years
Side Effects
- Flu-like symptoms (30–40%)
Pre-Treatment Assessment
- Renal function
- Vitamin D levels
- Correct deficiency before therapy
Indications for Treatment
Definite Indications
- Bone pain
- Preoperative preparation
- Hypercalcemia
- Progressive deformity
Possible Indications
- Early disease
- Skull involvement
- Risk of neurological complications
Asymptomatic Patients
- Consider treatment if:
- High-risk bones involved
- Early disease detected
Surgical Management
Indications
- Severe osteoarthritis ? joint replacement
- Bone deformity correction
- Fracture fixation
- Nerve decompression
Important Preoperative Step
- Use bisphosphonates to:
- Reduce vascularity
- Decrease intraoperative bleeding
Genetics
Gene Involved
- SQSTM1 (p62)
Key Features
- Regulates osteoclast activity
- Autosomal dominant inheritance
- Incomplete penetrance
Possible Viral Association
Suspected Virus
- Measles virus
Evidence
- Viral-like inclusions in osteoclasts
Status
- Still controversial
Changing Prevalence
Observed Trend (e.g., England)
- 1970s: >8%
- 1990s: ~2%
- Recent: <1%
Possible Explanation
- Introduction of measles vaccination
Key Takeaways
- Paget disease is a disorder of abnormal bone remodeling
- Often incidentally detected
- Elevated alkaline phosphatase is a key clue
- Zoledronic acid is the treatment of choice
- Early treatment prevents deformity and complications
- Disease prevalence has declined significantly
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