Paget's disease of bone

Question 1

What is Paget’s disease of the bone?

Answer 1

A focal disorder of bone remodelling due to the excessive activity of osteoblasts and osteoclasts

Question 2

Briefly describe the pathophysiology of Paget’s.

Answer 2

1. Excessive bone turnover (formation + resorption) due to excessive osteoblast + osteoclast activity.
2. Leads to patchy areas high density (sclerosis) + low density (lysis).
3. Enlarged + misshapen bones → risk of fracture.
4. Partic affects the axial skeleton (bones of the head and spine).

Question 3

Describe the epidemiology of Paget’s.

Answer 3

• Over 40
• Triggered by infection
• Genetic link
• F > M

Question 4

Describe the clinical presentation of Paget’s.

Answer 4

Bone pain
Bone deformity
Fractures
Hearing loss (if bones of ear affected)

Question 5

What are the 3 phases of Paget’s disease?

Answer 5

1. Lytic: excessive osteoclast activity - more bone resorption
   = low density bone
2. Lytic + blastic (mixed) – excessive osteoclastic bone resorption and disorganised osteoblastic bone formation
   = patchy lysis and sclerosis
3. Blastic (latent) - osteoblasts lay down weak new bone - disorganised osteoblastic bone formation

Question 6

Give 3 things seen on a X-ray for Paget’s.

Answer 6

1. Bone enlargement + deformity
2. Osteoporosis circumscripta (well defined osteolytic lesions)
3. Cotton wool appearance of skull (poorly defined areas of sclerosis + lysis)
4. V-shaped defects in long bones

Question 7

What would a blood test show for Paget’s?

Answer 7

1. Raised ALP -> other LFTs are normal (monitoring of this in future as effective treatment should normalise the ALP and eliminate symptoms)
2. Normal calcium + phosphate

Question 8

Treatment for Paget’s.

Answer 8

1. 1st line - Bisphosphonates
   - e.g. IV/ORAL ZOLENDRONATE or ORAL ALENDRONATE
   - which inhibit bone resorption by decreasing osteoclast activity
2. NSAIDs e.g. IBUPROFEN for pain
3. Calcium + Vitamin D supplements particularly whilst on bisphosphonates

• Disease activity monitored by symptoms and measurement of serum
  alkaline phosphatase or urinary hydroxyproline