Degeneration into osteosarcoma is a rare but almost invariably fatal complication of Paget disease, with an incidence of 0.2% to 1%.7 It clinically manifests as increased bone pain that is poorly responsive to medical therapy, local swelling, and pathologic fracture.8
Radiography is key to the work-up
The diagnosis of Paget disease is primarily radiographic. Early in the disease process, lytic lesions with thinning of the cortex will be noted. Later in the disease, there will be a mixed lytic/sclerotic phase, in which enlargement of the bone, a thickened cortex, and coarsened trabeculae are observed.
Characteristic radiographic findings. Focal lytic lesions in the skull are known as osteoporosis circumscripta. In the sclerotic phase, there is a thickening of the calvaria (termed “cotton wool”). Lesions involving the long bones will begin at the proximal or distal subchondral region and progress toward the diaphysis, with a sharp oblique delineation between involved bone and normal bone; this is described as “blade of grass” or “flame-shaped.”9
Within the pelvis, there will be cortical thickening and sclerosis with enlargement of the iliac wing. Within the spine, there will be enlarged vertebrae with a thickened sclerotic border, resulting in a “picture frame” appearance. Later in the disease, the sclerosis will involve the entire vertebrae (termed “ivory vertebra”).10
Additional testing options include magnetic resonance imaging (MRI), bone scintigraphy, laboratory testing, and biopsy.
Continue to: MRI is recommended...