Children and adults with FD/MAS who visited at least once in our center (outpatient and hospitalized patients).

and with the first visit in the center included between 1996 and 2006 - before certification of our center.

Children and adults with FD/MAS who visited at least once in our center (outpatient and hospitalized patients).

and with the first visit in the center included between 2007 and 2019 - after certification of our center.

Evaluation and analysis of clinical data (baseline demographic features (sex, age at diagnosis, age at first symptoms, age at first visit), initial presenting symptoms, affected bone sites (monostotic FD or polyostotic FD), renal phosphate wasting, MAS, Mazabraud syndrome, endocrine disease, fractures, bone specific treatment especially bisphosphonate and surgery, pain and disease's severity.

The main objective was to compare time elapsed between first symptomes or discovery of bone lesions and the diagnosis of FD, over 2 periods of time: 1996-2006 (before certification) and 2007-2019 (after certification).