Answer: The correct answer is Paget disease. Although diffusely sclerotic vertebra may occur with lymphoma and breast cancer, expansion of the vertebral body is not seen. In renal osteodystrophy, marked sclerosis occurs primarily at the endplates, which leads to a striped appearance, referred to as the "rugby jersey" sign.
Findings: Diffuse sclerosis and enteroposterior/ lateral expansion of the C7 vertebral body. Vertebral body height is preserved and there is no involvement of the adjacent vertebra.
Discussion: Although the differential for diffusely sclerotic vertebral body, or "ivory vertebra" includes lymphoma, blastic metastases, and Paget disease, only Paget disease has the additional findings of vertebral body expansion.
In adults, the most common cause of diffusely sclerotic vertebra areosteoblastic metastases from breast or prostate cancer. Other metastatic diseases to consider include lymphoma, plasmacytoma, chordoma, and primary bone sarcomas.
Paget disease may also present with an ivory vertebral body; however, a distinguishing feature is expansion of the vertebral body, which when present (seen in 63% of cases) allows definitive differentiation of this disease from other causes. Expansion occurs as a result of endosteal and periosteal bone remodeling, usually periosteal apposition (new bone formation) and endostealresorption (bone absorption). Expansion does not occur in the craniocaudal dimension, because vertebral end plates do not have a true bony cortex (i.e. no periosteum/ endosteum interface) and therefore do not undergo such bone remodeling. Although there is no expansion at the end plates, thickening and hypertrophy of the trabecullar bone parallel to the end plates does occur, which may appear similar to a thickened cortex. The combination of thickening of the endplates and cortical remodeling leads to the "picture frame" appearance on lateral radiographs in the earlier phases of disease. Further progression of these processes leads to a diffusely sclerotic vertebra seen in this case.
Paget disease is usually seen in older people. The spine is the second most commonly affected site after the pelvis. Involvement of the cervical spine, as seen in this case, is relatively rare (14%), compared to the lumbar spine (58%) and thoracic spine (45%).
In children, diffusely dense vertebral bodies are rare, and typically occur from lymphoma, usually Hodgkin lymphoma. Less frequently, they may be seen with osteosarcoma, osteoblastoma, or metastatic neuroblastoma, medulloblastoma, or Ewing sarcoma.
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