Fact-sheet: Paget disease


Updated on 02/17/2022 at 4:05 PM

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Definition

Benign, deforming osteodystrophy of the elderly, of unknown etiology, involving one or more bones, characterized by excessive bone remodeling leading to progressive hypertrophy of the affected bones and significant abnormalities of bone microarchitecture.

Clinical features

Sometimes an incidental finding. Usually, at onset, mechanical bone pain: low back pain, limping, limb pain. Any part of the skeleton can be affected. Progressive hearing loss (petrous bone involvement). Sometimes: - bone deformity (thickening, bowing) - local vasomotor disturbances (increased skin warmth over affected bones). - skull enlargement. Complications: bone fissuring or fracture, degenerative joint involvement (hip, knee), spinal cord compression (vertebra).

Laboratory findings

Calcemia, phosphatemia and calciuria: normal results
Increased serum alkaline phosphatase
Increased 24-hour urinary hydroxyprolinuria

Radiography

3 typical imaging features of Paget disease:

  • cortico-trabecular dedifferentiation
  • thickening of the bone trabeculae
  • vertebral body enlargement (the spinal canal may narrow)

ALL VERTEBRAE ARE INVOLVED

Frontal radiograph

The spinous process is involved and the pedicles are further apart ("hypertelorism").

CT

Used when there is diagnostic uncertainty.
Thickening of the cortical bone, which is either very dense or, conversely, fibrillar with loss of corticomedullary differentiation.
Bony trabeculae are fewer in number but thicker and disorganized, with an areolar or honeycomb appearance.
Persistence of areas of fatty density between the bony trabeculae.
Very dense focal intramedullary areas with stellate margins.
Enlargement of the affected bone.

MRI

In case of doubt: MRI is performed. The marrow will be seen to remain bright on T1 (the marrow is not involved in Paget disease, unlike tumor).

In most cases, Pagetic lesions show fatty signal, particularly on T1.
In cases of intense bone resorption, fibrovascular tissue is present, hypointense on T1, hyperintense on T2, and enhancing markedly after gadolinium injection.
In highly active forms, edematous reaction of the soft tissues may be observed.
During the late inactive phase, focal areas of low signal on both T1 and T2 may be seen within the fatty signal of Pagetic bone, indicating areas of bone sclerosis.

Nuclear medicine

Increased uptake on technetium-99m bone scintigraphy.

Management

NSAIDs, analgesics (sometimes effective).
In case of refractory bone pain or complications: injectable thyrocalcitonin or oral bisphosphonates +/- calcium.
Orthopedic and surgical treatment: in case of fracture, bowed tibia, or spinal cord compression.

Differential diagnosis

In men: bone metastases from prostate cancer. Note: 1% risk of sarcomatous degeneration.

DDx of elevated alkaline phosphatase:

Osteomalacia

  • Paget disease
  • Growth
  • Major fractures
  • Bone metastases