Paget’s Disease of Bone

Paget’s disease of bone refers to a disorder of bone turnover. There is excessive bone turnover (formation and reabsorption) due to excessive activity of both osteoblasts and osteoclasts. This excessive turnover is not coordinated, leading to patchy areas of high density (sclerosis) and low density (lysis). This results in enlarged and misshapen bones with structural problems that increase the risk of pathological fractures. It particularly affects the axial skeleton (the bones of the head and spine).

Presentation

Paget’s disease typically affects older adults. It presents with:

  • Bone pain
  • Bone deformity
  • Fractures
  • Hearing loss can occur if it affects the bones of the ear

 

Key Investigations

Xray Findings

  • Bone enlargement and deformity
  • Osteoporosis circumscripta” describes well defined osteolytic lesions that appear less dense compared with normal bone
  • Cotton wool appearance” of the skull describes poorly defined patchy areas of increased density (sclerosis) and decreased density (lysis)
  • V-shaped defects” in the long bones are V shaped osteolytic bone lesions within the healthy bone

 

Biochemistry

  • Raised alkaline phosphatase (and other LFTs are normal)
  • Normal calcium
  • Normal phosphate

 

Management

Bisphosphonates are the main treatment. They are generally very effective. They interfere with osteoclast activity and seem to restore normal bone metabolism. They improve symptoms and prevent further abnormal bone changes.

Other measures include:

  • NSAIDs for bone pain
  • Calcium and vitamin D supplementation, particularly whilst on bisphosphonates
  • Surgery is rarely required for fractures, severe deformity or arthritis

 

Monitoring involves check the serum alkaline phosphatase (ALP) and reviewing symptoms. Effective treatment should normalise the ALP and eliminate symptoms.

 

Complications

Two key complications to remember are:

  • Osteogenic sarcoma (osteosarcoma)
  • Spinal stenosis and spinal cord compression

 

Osteosarcoma is a type of bone cancer with a very poor prognosis. It presents with increased focal bone pain, bone swelling or pathological fractures. The risk is increased in Paget’s disease and patients need to be followed up to detect it early. They can usually be seen on a plain xray.

Spinal stenosis may occur where deformity in the spine leads to spinal canal narrowing. If this presses on the spinal nerves it causes neurological signs and symptoms. This is diagnosed with an MRI scan and is often treated effectively with bisphosphonates. Surgical intervention may be considered.

 

Last updated April 2019
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