May present with angular deformity or pathologic fracture. Most commonly, involves the lower limbs and is usually asymmetric. The cortex of the affected bone may be thinned by endosteal erosion which creates a scalloped pattern. In long bones, the lesions are usually metaphyseal in location, extending into the rnid-diaphysis. An angular deformity in the bone is often present at the level of the lesion.
Periosteal reaction is absent except when a pathologic fracture is present.
Bone scans show increased uptake-can assess the extent and multiplicity of involvement. CT scan is helpful in differentiating eosinophilic granuloma, osteomyelitis, and unicameral bone cyst. Few studies other than plain X-rays are required in a typical case of polyostotic disease. Fibrous dysplasia is composed of fibrous stroma with normal appearing nuclei and irregular shaped strands of osteoid and bone. There are few if any osteoblasts, the osteoid and bone seem to arise directly from the background of fibrous stroma.