Geels RES, Meier ME, Saikali A, et al. - Fibrous dysplasia/McCune-Albright Syndrome (FD/MAS) patients experience long bone fractures in relation to a higher skeletal burden score and MAS hyperthyroidism.

• From 2 large, well-phenotyped cohorts (NIH and LUMC), data were analyzed for 419 patients to identify long bone fractures at FD sites.

• Occurrence of ≥1 lifetime fracture was evident in 48 (59%) patients, and median age at first fracture was 8 years.

• A peak in fracture rates occurred between 6–10 years of age, followed by a decline thereafter.

• Lifetime fracture rate was found to be related to skeletal burden score and MAS hyperthyroidism.

• Factors linked with a higher total number of lifetime long bone fractures were skeletal burden score > 25 and age at first fracture ≤7 years, and both these factors may predict a more severe clinical course.