Polyostotic fibrous dysplasia (PFD) is a sporadic disorder which affects multiple sites in the skeleton. The bone at these sites is rapidly reabsorbed and replaced by abnormal fibrous tissue or mechanically abnormal bone. PFD may occur alone or as part of the McCune-Albright Syndrome (MAS), a syndrome originally defined by the triad of PFD, cafe-au-lait pigmentation of the skin, and precocious puberty. The bony lesions are frequently disfiguring and painful, and depending on the location of the lesion, can cause significant morbidity. Lesions in weight-bearing bones can lead to disabling fractures, while lesions in the skull can lead to compression of vital structures such as cranial nerves.

The natural history of this disease is poorly described and there are no clearly-defined systemic therapies for the bone disease. The purpose of this study is to define the natural history of the disease with or without treatment.