Paget's Disease of Bone

Aka: Paget's Disease of Bone, Paget's Disease, Osteitis Deformans

1. Epidemiology
   1. Onset over age 50 years
   2. Prevalence (United States)
      1. Overall: 3%
      2. Age over 80 years: 10%
   3. Ethnicity
      1. Rare in Asia
      2. Common in United States, Australia, and New Zealand
2. Pathophysiology
   1. Associated factors (etiology unknown)
      1. Viral antigen association (especially Measles)
      2. Family History (Chromosome 18q)
   2. Phases
      1. Phase 1: Intense Osteoclastic activity
         1. Bone resorption predominates
         2. Bone turnover is 20 times normal rate
      2. Phase 2: Osteolytic-Osteoblastic activity
         1. Woven bone formation
         2. Ineffective mineralization
      3. Phase 3: Dense bone deposition
         1. Bone is disorganized and sclerotic
         2. Weaker than normal bone
   3. Distribution
      1. Pelvis (72%)
      2. Spine
         1. Lumbar (58%)
         2. Thoracic (45%)
         3. Cervical (14%)
      3. Skull (42%)
      4. Long bones
         1. Femur (55%)
         2. Tibia (35%)
         3. Humerus (31%)
3. Symptoms (Asymptomatic in 70% of cases)
   1. Constant pain
   2. Pain provocative factors
      1. Rest or night pain
      2. Weight bearing
      3. Warming
4. Signs
   1. Kyphosis
   2. Limb shortening or bowing
   3. Frontal forehead bossing
   4. Skull enlargement
   5. Loose teeth
5. Labs
   1. Alkaline Phosphatase
      1. Total serum Alkaline Phosphatase
      2. Bone specific Alkaline Phosphatase
   2. Urinary hydroxyproline no longer used as marker
6. Radiology: XRay
   1. General changes
      1. Combined lytic lesions with nearby sclerosis
   2. Skull changes
      1. Osteoporosis circumscripta
   3. Long bone changes
      1. Flame-shaped changes
      2. Limb bowing
      3. Fractures (banana-shaped transverse Fractures)
7. Radiology: Bone Scan (Technetium-99m)
   1. Focal areas of uptake
   2. Appearance of Mouse-face on Vertebrae
8. Monitoring
   1. Screening if first degree relative has Paget's Disease
      1. Alkaline Phosphatase every 3 years (over age 50)
   2. Monitoring of diagnosed Paget's Disease
      1. Alkaline Phosphatase every 3 to 12 months
9. Associated conditions
   1. Malignant degeneration (up to 10% of Paget's Disease)
      1. Osteosarcoma
      2. Fibrosarcoma
      3. Spindle cell Sarcoma
   2. Pseudomalignancy (Pseudosarcoma or pseudo giant cell)
   3. Osteoarthritis (Paget's Disease involving joint)
   4. Nephrolithiasis
   5. Nerve compression syndromes from direct pressure
      1. Hearing Loss
      2. Spinal stenosis
      3. Neuropathic pain, weakness or Paresthesias
10. Management: General Measures
    1. Adequate pain control
    2. Calcium Supplementation 1500 mg qd
    3. Vitamin D 400 IU per day
    4. Low impact Exercise
    5. Avoid straining affected bone
11. Management: Suppress bone resorption (Osteoclasts)
    1. Indications
       1. Symptomatic patients
       2. Alkaline Phosphatase >125 to 150% of normal
    2. First line agents: Bisphosphonates
       1. Alendronate (Fosamax) 40 mg qd for 6 months
       2. Pamidronate (Aredia) intravenous
    3. Alternative agents (not as potent as Bisphosphonates)
       1. Calcitonin 100 U SC or IM qd for 6 to 18 months
12. References
    1. Simon in Klippel (1997) Primer Rheumatic, p. 382-4
    2. Schneider (2002) Am Fam Physician 65(10):2069-72