paget's%20bone%20disease
PAGET'S BONE DISEASE
Paget's bone disease, also known as osteitis deformans, is characterized by a significant increase in bone resorption and turnover in localized parts of the skeleton causing enlargement and thickening of the bone that is disordered and architecturally unstable.
The prevalence increases with age, with men and women affected equally.
Genetic factors and/or viral infection may play a role in the etiology.
May affect one bone (monostotic) or several bones (polyostotic).
By decreasing frequency, involved bones may include pelvic bone and sacrum, spine, skull and femur, tibia, humeri and clavicles.

Principles of Therapy

  • Goals of treatment are to ease pagetic pain, reduce activity of the disease, obtain full remission and prevent complications
  • Important to note the location of the pagetic bone lesion and presence of comorbidities in treating asymptomatic patients
    • May initiate treatment if the serum alkaline phosphatase (ALP) level is >2-4x the upper limit of normal (ULN) value
  • Patients should receive adequate doses of Ca (1500 mg/day) and Vit D (800 units/day) to avoid hypocalcemia
  • Patient should receive pharmacotherapy prior to elective surgery on pagetic site
  • Response to therapy is guided by the following factors:
    • Pain reduction
    • Decrease in serum ALP level and normalization of other bone turnover markers
    • Abnormal bone replacement with normal lamellar bone
    • Radiographic healing
    • Improvement in patient’s quality of life

Pharmacotherapy

Antiresorptive Therapy

Bisphosphonates

  • Eg Alendronic acid, Etidronic acid, Pamidronic acid, Risedronic acid, Tiludronate, Zoledronic acid
  • Inhibit osteoclast activity and decrease bone resorption
  • Decrease bone pain, improve neurological complications, stabilize hearing loss, heal bone lesions
    • Biochemical effects: Decrease by 50% of serum ALP concentrations and urinary excretion of hydroxyproline, pyridinoline and collagen-derived N-telopeptides
    • Prolonged effectiveness; effects remain after years of withdrawal
    • Relatively safe with variable side effect profiles among different bisphosphonates
  • Recommended for active Paget’s bone disease patients at risk of future complications and prior to surgery of pagetic bone
  • Bisphosphonates may be used in patients presenting with fracture secondary to pagetic bone lesion
    • May be administered once the patient is stable
  • Zoledronic acid is the most potent bisphosphonate approved in the United States for Paget’s bone disease
    • Biochemical remissions are sustained and can last up to 1-2 years in most patients
    • Preferred drug because of its efficacy especially in patients with more extensive disease and those who are already on several drug treatment for other conditions
  • Pamidronic acid is an alternative intravenous agent but is less potent and takes longer to infuse compared with Zoledronic acid and some patients may develop drug resistance
  • Risedronic acid is more effective than Etidronic acid
    • Preferred in younger patients with limited disease
  • Alendronic acid is more effective than Pamidronic acid in patients previously treated with other bisphosphonates
    • Alendronic acid is also more effective than Etidronic acid
    • Also preferred in younger patients with limited disease
  • Neridronate is a nitrogen-containing bisphosphonate with comparable efficacy to Zoledronic acid as shown in a randomized trial and can be given intravenously or intramuscularly but is available only in some countries
  • Associated with possible risk of atypical subtrochanteric and diaphyseal femur fractures

Calcitonin

  • 32 amino acid hormone secreted by C cells of the thyroid gland
  • Inhibit osteoclast activity and decrease bone resorption
  • Alternative for patients who cannot tolerate bisphosphonates or when bisphosphonates are contraindicated
  • Decrease bone pain, improves neurological complications, stabilizes hearing loss, heals bone lesions
    • Biochemical effect: Up to 30-50% decrease in serum ALP and urinary hydroxyproline within 3-6 months and remain at these levels as long as treatment continues
    • Short-lived effectiveness; recurrences occur rapidly after withdrawal; high incidence of adverse effects (nausea, flushing)

Pain Management

  • Resorptive therapy generally relieves pagetic pain
  • Manage pain due to bone deformity, arthritis or neurological complications
  • Relieve pagetic pain in addition to resorptive therapy

Paracetamol (Acetaminophen)

  • Analgesic with antipyretic properties

Nonsteroidal Anti-inflammatory Drugs (NSAIDs)

  • Act as non-selective inhibition of cyclooxygenase (COX)-1 and COX-2 pathway
  • Have analgesic, anti-inflammatory and antipyretic properties

COX-2 Inhibitors

  • Selective inhibition of COX-2 pathway without inhibiting COX-1 pathway
  • Have analgesic, anti-inflammatory and antipyretic properties with reported improved gastrointestinal (GI) tolerance

 

Management of Complications of Paget's Disease of the Bone

Hearing loss

  • It is suggested to use a potent bisphosphonate to prevent worsening of hearing deficit

Osteoarthritis

  • The use of analgesics is suggested as an adjunctive therapy for mild-to-moderate joint pain caused by joint cartilage deterioration
  • In patients with severe osteoarthritis, bisphosphonate therapy is recommended before undergoing elective total joint replacement

Paralysis

  • Immediate treatment with a potent intravenous (IV) bisphosphonate is suggested along with neurosurgical consultation
  • Due to correction of ischemia, most patients with paralysis recover well after medical therapy
  • But in cases of severe structural damage, surgery may be required although the outcome may not be always optimal

Bowing of lower extremity

  • A potent bisphosphonate prior to elective surgery is suggested on patients requiring an osteotomy to correct severe bowing of the lower extremity

Neoplasms

  • Osteosarcoma or a giant cell tumor patients should be evaluated by an orthopedic surgeon
  • For planned surgery, pretreatment with a potent bisphosphonate is suggested to reduce bleeding from adjacent pagetic bone

Congestive heart failure

  • An effective treatment improves the symptoms
  • Bisphosphonate treatment in patients with Paget's disease with congestive heart failure is recommended

Non-Pharmacological Therapy

Physical Therapy

  • Improves muscle strength to help control certain types of pain
  • Helps to maintain flexibility and joint range of motion, increase endurance and avoid deconditioning
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