[Fibrous dysplasia: differential diagnosis from Paget's disease]

A 27-year-old woman presented with chronic diffuse bone pain and skeletal deformities. Since the age of 3 years she had occipital hyperostosis. Since aged 13 years she had symptoms indicating spinal root involvement due to hyperkyphosis. For the last 6 years there was evidence of destructive and hyperplastic changes in the region of the middle ribs. Alkaline phosphatase (APL) had been elevated (> 250 U/l) for several years. Three years before the present admission the patient had been hospitalized elsewhere because of bone pain and had received intermittent infusions of pamindronate to a total of 600 mg.

Laboratory tests showed moderate rise in bone-specific APL and osteocalcin. Conventional x-ray examinations and computed tomography showed lesions in the occipital bone, sella turcica and ethmoid air cells. Several thoracic vertebral fractures were demonstrated. Skeletal scintigraphy indicated enrichment in the occipital and supraorbital regions, as well as in vertebrae and ribs. Dual energy x-ray absorptiometry (DEXA) showed osteopenia. Bone biopsy from the occipital lesion revealed fibrous dysplasia.

The diagnosis of fibrous dysplasia having been confirmed, cyclical treatment with i.v. pamidronate was given for 6 months. It was well tolerated and lessened the pain without changing the objective findings.

In case of uncertain radiological and scintigraphic findings in the differential diagnosis of fibrous dysplasia, Paget's disease or bone tumor, it is essential to obtain a biopsy and, if available, perform gene analysis.