Paget's Disease of the Bone

Question 1

What is the epidemiology of Paget’s?

Answer 1

Second most common bone disorder – 1-3% >55yrs in the UK

Increases incidence with age

Slight male predominance - 3:2

Question 2

What is the aetiology and pathophysiology of Paget’s?

Answer 2

Genetic component (some AD inheritance in some families) + environmental factor e.g. mechanical stress, ?infection (measles, RSV)

Osteoclasts and blasts changes:

• Clasts = greater number and larger
• Blasts = greater number and over active due to increased factors released by clasts
• Leads to accelerated bone turnover rate (lytic phase) and subsequent rapid bone formation (sclerotic phase)
• New bone is disorganised, larger and more prone to fracture

Has a predilection for the axial skeleton e.g. lumbosacral spine + pelvis, also skull, femur and tibia; hands and feet rarely affected

Chronic and progressive

Question 3

How does Paget’s present?

Answer 3

Commonly asymptomatic + an incidental finding on XR or a raised alk phos

Symptoms:

• Bone pain (at rest, night and movement; not focused on a joint)
• Deformity
• Pathological fracture
• Osteoarthritis
• Spinal stenosis, cauda equina
• Greater risk of osteosarcoma

Often affects either 1 (1/3rd) or 2 (2/3rds) bones

Question 4

How do you investigate Paget’s?

Answer 4

Bloods:

• Alk phos - high
• Ca, phosphorus, PTH - normal (but if immobilised, may lead to hypercalcaemia)

XR:

• Osteolysis = radiolucency/dark/less dense + sclerosis = radioopaque/light/more dense areas
• ‘blade of grass lesion’ = V-shaped pattern between healthy and diseased long bones
• ‘cotton wool’ pattern in skull = multifocal sclerotic patches

Radionuclide scans can show extent of disease

Bone biopsy needed if malignant change suspected

Question 5

How do you manage Paget’s?

Answer 5

Pain control + prevention of progression and complications

Pain:
- NSAIDs + paracetamol

Progression:

• Bisphosphonates PO/IV (zoledronate = used commonly as higher rates of remission + longer duration of suppression off a single IV dose); Vit D + Ca supplementation
• Calcitonin SC - for short periods in those intolerant to bisphosphonates (as associated risk of malignancy with long term use) - keeps ‘calcium in the bones’ by opposing PTH

Serial monitoring of Alk phos to assess treatment efficacy

Surgery may be required to manage deformity or complications

Orthotic devices, sticks and walkers may be useful in leg disease

Question 6

What monitoring is required for Paget’s?

Answer 6

Monitored indefinitely for presence of osteosarcoma

Presentation of osteosarcoma is classically: - Increased bone pain that is poorly responsive to medical treatment

• Local swelling
• Pathological fracture

X-ray and bone biopsy can help to confirm the diagnosis