- AKA osteitis deformans
- Important not to confuse its imaging appearance with those of other diseases.
- Complications of Paget disease include:
- Deformity and
- Neurologic symptoms
- Neoplastic transformation
- Paget disease is extraordinarily common, affecting 3%–4% of the population over 40 years of age and up to 10%–11% after 80 years of age.
- Although Paget disease is unusual in people younger than 40 years of age.
- Paget disease is characterized by excessive and abnormal remodeling of bone, with both active and quiescent phases.
- Three phases
- Lytic phase (incipient-active), in which osteoclasts predominate
- Mixed phase (active), in which osteoblasts begin to appear
- Blastic phase (late-inactive), in which osteoblastic activity gradually declines
- Paget disease is predominantly located in the axial skeleton, with the most commonly affected sites being the pelvis (30%–75% of cases), spine (30%–75%), and skull (25%–65%)
- Proximal long bones are also frequently involved, with the femur affected in 25%–35% of cases (2–5). Less commonly affected sites include the shoulder girdle and forearm (humerus, 31% of cases; scapula, 24%; and clavicle, 11%).
- Involvement of other sites, including the ribs, fibula, bones of the hands and feet, calcaneus, patella, and tibial tubercle, is infrequent.
- Monostotic disease (10%–35% of cases) is more often seen in the axial skeleton, although any site can be the sole region of involvement.
- Polyostotic disease (65%–90%) is more frequent than monostotic disease, tends to have right-sided predominance, and usually involves lower extremities
 Imaging Findings
 Plain films
- The early phase of Paget disease is characterized by osteolysis
- In the skull, osteolysis is frequently seen as well-defined, often large areas of radiolucency most commonly affecting the frontal and occipital bones; these areas are referred to as osteoporosis circumscripta or osteolysis circumscripta.
- Both inner and outer calvarial tables are involved, with the former usually more extensively affected.
- This pattern is in contradistinction to that of fibrous dysplasia, which usually affects the outer table more prominently.
- In the long bones, osteolysis begins as a subchondral area of lucency.
- The advancing wedge of osteolysis often demonstrates a characteristic sharp radiolucent margin without sclerosis likened to a blade of grass or flame.
- In rare cases, the disease is isolated to the diaphysis, most commonly in the tibia, rather than subchondral bone, which can cause diagnostic confusion
- Vast majority of cases of Paget disease seen by radiologists are in the mixed phase.
- Characteristic manifestations seen radiographically are coarsening and thickening of the trabecular pattern and cortex.
- Trabecular thickening occurs primarily along the lines of stress, although disorganized areas are also seen.
- Paget disease of the pelvis usually manifests with cortical thickening and sclerosis of the iliopectineal and ischiopubic lines.
- These findings are often asymmetric and more commonly seen on the right side.
- These manifestations are also often associated with enlargement of the pubic rami and ischium.
- Paget disease of the spine frequently manifests with cortical thickening encasing the vertebral margins, which gives rise to the "picture frame" appearance on radiographs in mixed phase disease.
- The osteoblastic activity is seen along all four margins of the vertebral body cortices, unlike the rugger jersey vertebrae in renal osteodystrophy, which only involves the superior and inferior endplates.
- The vertical trabecular thickening pattern in Paget disease is coarser than the more delicate pattern seen in hemangiomas with which it can be confused.
- Flattening or squaring of the normal concavity of the anterior margin of the vertebral body can be seen on the lateral spinal radiographs.
Patient #3: Malignant transformation of Paget disease (osteosarcoma).
 See Also
 External Links
- Stacy E. Smith, Mark D. Murphey, Kambiz Motamedi, Michael E. Mulligan, Charles S. Resnik, and Francis H. Gannon. From the Archives of the AFIP: Radiologic Spectrum of Paget Disease of Bone and Its Complications with Pathologic Correlation. RadioGraphics 2002 22: 1191-1216.
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