Paget's Disease

Question 1

Definition

Answer 1

Condition characterised by increased osteoclast activity = excessive bone turnover followed by excessive osteoblast activity
- Patchy areas of high density (sclerosis) and areas of low density (lysis)
- Large misshapen bones with increased risk of pathological fractures
- Particularly affects axial skeletons

Question 2

Epidemiology + Riskfactors

Answer 2

Age: mean onset 55 years
Family history
Infection: paramyxoviruses

Question 3

Aetiology

Answer 3

Linked to genetic mutation = SQSTMI

Question 4

Pathophysiology

Answer 4

Paget’s disease typically progresses through three stages
1. Initial osteoclastic activity leading to bone resorption
2. Mixed osteoclastic and osteoblastic activity resulting in deposition of structurally abnormal bone
3. Chronic, sclerotic phase in which bone formation supersedes bone resorption
Can have a dormant phase or “burned out state” where osteoclastic activity decreases

Question 5

Signs

Answer 5

• Bony deformities: skull bossing, bone bowing, prognathism
• Kyphosis
• Pelvic asymmetry
• Pathological fracture
• Reduced visual acuity: if CN II involvement (rare)
• Local temperature rise: due to increasing metabolic activity

Question 6

Symptoms

Answer 6

• Bone pain: femur/pelvis 75% of patients, skull involvement 37%
• Facial pain: if skull disease with CN V involvement
• Hearing loss: if skull disease with CN VIII involvement

Question 7

Diagnosis

Answer 7

Plain film x-ray:
- early-stage = osteolytic lesions, fractures,
- late phase = sclerotic changes, osteoporosis circumscripta, COTTON WOOL SKULL (areas of scleorsis + lysis)
Urinalysis: increased markers of collagen degradation, e.g. hydroxoproline
Bloods: high ALP

Question 8

Treatment

Answer 8

Asymptomatic:
- Observation: regular follow-up, education, e.g. regarding high-risk activities

Symptomatic or high-risk:
- FIRST LINE = Bisphosphonates: zoledronic acid or alendronic acid to reduce osteoclastic activity
- SECOND LINE = Calcitonin
- Supportive measures: education, analgesia, orthoses, walking aids

Severe disease:
- Surgery: i.e. total hip replacement for severe hip disease

Question 9

Complications

Answer 9

Arthritis
Hearing loss/tinnitus: if cranial nerve VIII involvement
Spinal stenosis: narrowing of the spinal canal with spinal involvement
Oesophagitis: secondary to bisphosphonate use
Pathological fractures: more common in long bones
Osteosarcoma: rare