ABSTRACT
The fibrous osseous dysplasia is a rare congenital condition characterised by the replacement of the medullary canal spongy os by a fibrous tissue proliferation. we reported a case of a young girl, 21 years old, who suffered from thoracic pain since more than one year, with apparation of the axillary arch which progressivaly increase in volume since six months. Examination revealed a fixed hard tumefaction, the thoracic radiography showed two souffle osteolytic images near the medium arc of the fifth left rib and fourth right rib. The osseous scintigraphy revealed an hyperfixation touching the right hemiface. The cranio-facial scan showed an interesting aspect of [frosted glass] of the clivus. The remodeling mark dosage of the osseous alkaline phosphatase was of 2321U/L. A mass biopsy was done which confirmed the diagnosis. the combination of costal and clivus fibrous dysplasia which had been never reported in literatures and the difficult therapeutic decision in front of this polystotic picture makes our case a particular case