Dr. Kevin Yip

Dr Kevin Yip
Orthopaedic Surgeon
MBBS(UK), FRCS(EDIN), FAM(SING), FHKCOS(ORTHO)

Featured on Channel NewsAsia

Paget Disease

Basics
Description
  • First described by Sir James Paget in 1877 , Paget disease (osteitis deformans) is a bone disorder commonly seen in the geriatric population.
  • As implied by the name osteitis deformans, the involved bone may be severely deformed and enlarged, features that suggest an inflammatory origin.
  • A chronic and slowly progressive disease of disorganized bone remodeling
  • Can affect any bone
  • Often asymmetric process
  • May involve one bone (monostotic) or multiple bones (polyostotic)
  • Classification:
    • Active phase:
      • Early (lytic) phase: Purely bone destruction
      • Mixed phase: Both bone destruction and formation
      • Late (sclerotic) phase: Predominantly bone formation
    • Inactive phase (patients 60-90 years old):
      • Many patients have inactive disease with no radiographic progression, symptoms, or laboratory abnormalities.
Epidemiology
This disease of late adulthood is rarely seen before the 4th decade of life.

Incidence
  • It affects 3-4% of the population >50 years old and is slightly more common in males .
  • It is more common in Caucasians of Anglo-Saxon descent .
Prevalence
Its prevalence increases with advancing age, up to 5-15% by the 9th decade .
 
Risk Factors
  • 1st-degree relatives of affected persons
  • Advancing age
Genetics
Ample evidence exists to suggest that 1st-degree relatives of affected persons carry a higher risk (up to 7 times higher) of developing the disease than those without family history of the disease.

Etiology
  • Genetic associations have been identified.
  • Infectious (one of the paramyxoviruses): Some investigators believe that the cause is a slow virus because of the long incubation periods, absence of fevers, and involvement of a single organ system.
Diagnosis
Signs and Symptoms
  • Clinical manifestations depend on the severity of the disease and the site of involvement.
    • Pain:
      • Many patients are asymptomatic, but others have mild to severe bone pain.
      • Acute bone pain suggests pathologic fracture or malignant degeneration.
      • Usually constant and unrelated to activity
    • Frontal bossing and conductive hearing loss may be present.
    • If the spine is involved, the patient may develop spinal stenosis with or without radiculopathy.
    • Arthritis:
      • Pagetic arthritis is common in the hip and knee.
      • Patients have severe pain and difficulty in ambulating.
Physical Exam
  • The most common findings are bowing of the extremity and local warmth if the bone is subcutaneous, such as the tibia.
  • Restricted ROM is common in the hip in patients with pagetic arthritis.
Tests
  • The basic components of the diagnostic evaluation are:
    • History and physical examination:
      • The involved area is warm to the touch because of the increased vascularity of the underlying bone.
    • Laboratory tests
    • Plain radiographs
    • Bone scan to evaluate the extent of skeletal involvement
Lab
  • Increased serum alkaline phosphatase levels are noted.
  • The 24-hour urine may show an increase in collagen breakdown products (N-telopeptide or hydroxyl proline, pyridinoline cross links; normal in 5% of patients).
  • Serum calcium usually is normal unless concurrent generalized inactivity, hyperparathyroidism, hyperthyroidism, or malignancy is present.
Imaging
  • Radiography:
    • Plain films show enlarged bone with thick, coarsened trabeculae and sclerotic and lytic changes in the affected bone.
    • A flamed-shaped area of radiolucency strongly suggests an advancing edge of a pagetic lesion.
  • A hot technetium-99m methylene diphosphonate bone scan also is observed.
  • The bone scan will quantify the number of bones involved.
Pathological Findings
  • Highly vascular bone resulting from high turnover rate
  • Multiple pathologic fractures resulting from structurally weaker bone
  • Histologically, more numerous osteoclasts and less mature (but fully mineralized) bone
Differential Diagnosis
  • Metastatic cancer
  • Fibrous dysplasia
  • Paget sarcoma
Treatment
General Measures
  • Therapy depends on the severity of the disease: Not all patients require treatment.
  • Indications for treatment include bone pain, high-output cardiac failure, and prevention of pathologic fracture.
  • Pain from associated arthritis can be treated with NSAIDs.
  • A cane or walker may be used for gait stabilization.
  • Surgery is indicated for patients with severe arthritis who are refractory to medical management or for patients with impending pathologic fractures.
    • Preoperatively, medical therapy should be initiated to reduce disease activity, to minimize blood loss, and to optimize surgical outcome.
Special Therapy
Physical Therapy
Physical therapy may be used to improve the patient’s ambulatory ability before or after surgery.

Medication
  • Medical treatment should be initiated for symptomatic patients or in preparation for orthopaedic surgery to prevent perioperative hypercalcemia or excessive bleeding.
    • Calcitonin:
      • Inhibits bone resorption by direct action on osteoclasts
      • Side effects include nausea, facial flushing, and polyuria.
  • Diphosphonates (commonly used):
    • Potent inhibitors of bone resorption
    • Bind to hydroxyapatite crystals in bone and thereby prevent osteolysis
    • Also may function as metabolic poisons for osteoclasts
    • Common side effects include nausea, vomiting, and loose bowel movements.
Surgery
  • Surgery usually is undertaken for 1 of 3 reasons:
    • Replacement of an arthritic joint
    • Internal fixation of a long-bone fracture
    • Correction of a long-bone deformity
  • Total hip and knee arthroplasty is extremely effective in relieving pain and improving function.
  • Intramedullary nails are the main modality for fixing long-bone diaphyseal fractures.
    • Multiple osteotomies may be necessary to correct the deformities.
Follow-up
Prognosis
  • Most patients with Paget disease are asymptomatic and have a normal life expectancy.
  • Long-term survival for patients with Paget sarcoma (<1% of patients with Paget disease) is poor: ~20% survival in 5 years .
Complications
  • Pathologic fractures
  • High-output cardiac failure
  • Malignant degeneration (Paget sarcoma)
Patient Monitoring
  • Patients usually are followed once a year.
  • Usually, plain radiographs are obtained.
Miscellaneous
Codes
ICD9-CM
731.0 Paget disease of bone
 
Patient Teaching
  • Patients should be well informed about their disease and the goals of treatment.
  • Treatment should be aimed at slowing or arresting disease progression, providing pain relief, or restoring function.
  • Appropriate consultations should be made to address any extraskeletal abnormalities (e.g., deafness).
  • The need for long-term follow-up should be emphasized.
  • Resources for patient education in the United States can be obtained from the Paget Foundation, 200 Varick Street, New York, NY 10014 (Telephone: 212-229-1502).
FAQ
Q: Are there effective treatments for Paget disease?
A: Diphosphonate therapy is very effective in halting bone resorption in Paget disease.

Q: Is hip replacement successful in patients with Pagetic arthritis of the hip?
A: Joint replacement surgery is an excellent method of relieving pain and improving function in patients with Paget disease of the hip.
 
Q: What are the warning signs of cancer in Paget disease?
A: Bone pain or the development of a soft-tissue mass are the earliest signs. Cortical bone destruction and a soft-tissue mass can be detected with CT or MRI.

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