Paget”s Disease:
Definition
Paget disease is a disorder of bone remodelling characterized by excessive
bone resorption followed by an increase in bone formation.
Etiology:
Some studies suggest a genetic linkage for Paget disease
located on chromosome arm 18q.
Although the etiology of Paget disease is unknown, both
genetic and environmental contributors have been suggested. Ethnic and
geographic clustering of Paget disease is well described.
Pathophysiology:
There is osteoclastic
overactivity followed by compensatory osteoblastic activity leads to a
structurally disorganized mosaic of bone (woven bone), which is mechanically
weaker, larger, less compact, more vascular, and more susceptible to fracture
than normal adult lamellar bone.
Clinical Features:
Approximately 70-90% of persons with Paget disease are
asymptomatic; however, a minority of affected individuals experience various
symptoms, including the following:
Bone pain (the most
common symptom)
Secondary
osteoarthritis (when Paget disease occurs around a joint)
Bony deformity (most
commonly bowing of an extremity)
Excessive warmth (due
to hypervascularity)
Neurologic
complications (caused by the compression of neural tissues)
Sites of involvement:
Paget disease may involve a single bone but is more
frequently multifocal. It has a predilection for the axial skeleton (ie, spine,
pelvis, femur, sacrum, and skull, in descending order of frequency), but any
bone may be affected.
After onset, Paget disease does not spread from bone to
bone, but it may become progressively worse at pre-existing sites.
Indications for Treatment :
Intolerable pain
Involvement of weight bearing joints
Neurological involvement
Hypercalcemia
Hypercalcinuria
Congestive Cardiac Failure
Management
Guidelines:
Several bisphosphonates : Alendronate,Risedronate and
Pamidronate are approved for treatment of Pagets”s Disease.
Six months of treatment with oral alendronate and two months
of treatment with oral risedronate lead to sustained remission in a large
number of patients.
Intravenous pamidronate canbe used for patients with
contraindications to use of oral bisphosphonates.
A 2014 Endocrine Society Clinical Practice Guideline on
Paget disease recommends the following :
Plain radiographs of
the pertinent regions of the skeleton in patients with suspected Paget disease
A radionucleotide
bone scan to determine the extent of the disease if the diagnosis is confirmed
Measurement of serum
total alkaline phosphatase or, when warranted, a more specific marker of bone
formation or bone resorption to assess the response to treatment or evolution
of the disease in untreated patients
Consider treatment
with a bisphosphonate for most patients with active Paget disease who are at
risk for future complications
Consider a single
5-mg dose of intravenous zoledronate as the treatment of choice in patients who
have no contraindication
Consider measurement
of a specific marker of bone formation and bone resorption in patients with
monostotic disease who have a normal serum total alkaline phosphatase
Consider serial
radionuclide bone scans to determine the response to treatment if the markers
are normal
Bisphosphonate
treatment may be effective in preventing or slowing the progress of hearing
loss and osteoarthritis in joints adjacent to Paget disease and may reverse
paraplegia associated with spinal Paget disease
Consider treatment
with a bisphosphonate before surgery on pagetic bone