Fibrous dysplasia/McCune-Albright syndrome (FD/MAS) is a rare and complex disorder caused by postzygotic variants affecting the GNAS gene. The clinical presentation is highly variable, ranging from isolated bone involvement to multisystem disease with endocrine abnormalities and other complications. Due to its rarity and heterogeneity, knowledge on the natural history of FD/MAS remains limited and standardized data collection is needed to improve understanding of disease progression and outcomes.

To develop a standardized dataset for natural history studies in patients with fibrous dysplasia/McCune-Albright syndrome, enabling systematic collection of clinical data across expert centres and supporting future research within rare bone disease networks.

An international multidisciplinary working group developed a standardized dataset for FD/MAS. The dataset was designed to capture key clinical characteristics, including demographic information, disease presentation, skeletal involvement, endocrine manifestations, complications, treatment approaches, and patient-reported outcomes. The dataset was developed within the framework of European collaboration between expert centres involved in the care of patients with rare bone conditions.

A comprehensive standardized dataset for FD/MAS natural history studies was developed, covering the main domains required to characterize disease presentation, progression, management, and outcomes. The dataset enables harmonized collection of clinical information across centres and provides a framework for comparing patient populations and identifying factors associated with disease severity and complications.

The development of a standardized FD/MAS dataset represents an important step towards improving knowledge of this rare and heterogeneous condition. Harmonized data collection across expert centres will facilitate natural history studies, support clinical research, and contribute to improved understanding and management of patients with FD/MAS.

Fibrous dysplasia/McCune-Albright syndrome is a rare disorder with substantial variability in clinical presentation and disease course. A standardized dataset enables international collaboration and consistent collection of clinical information, creating opportunities to better define natural history, identify unmet clinical needs, and improve patient care.