TOPLINE:

In 2024, the prevalence and incidence of fibrous dysplasia (FD) or McCune-Albright syndrome (MAS) among hospitalised patients in France were 5.36 and 2.58 patients per 1,000,000 inhabitants, respectively. Cases were more often polyostotic, and women and children were predominantly affected. Common treatments included bisphosphonates, phosphate supplements, and aromatase inhibitors.

METHODOLOGY:

• Researchers conducted a retrospective cohort study using data from the French National Health Data System to evaluate the prevalence and incidence of FD or MAS and determine the frequency of associated clinical manifestations.
• They analysed data of 2249 patients who were hospitalised with a primary or associated diagnosis of monostotic or polyostotic FD or MAS between 2012 and 2024; 63% were women, and 26% were children.
• The main objective was to estimate the prevalence and incidence of FD or MAS, and the secondary objectives included determining how prevalence and incidence differed according to patient characteristics such as age, sex, and the type of diagnosis.
• Manifestations associated with FD or MAS were assessed using hospitalisation diagnoses and outpatient drug dispensing data; the analysis was restricted to 2020-2024 data.

TAKEAWAY:

• In 2024, the prevalence of FD or MAS was 5.36 per 1,000,000 inhabitants. The prevalence was higher in children vs adults (7.96 vs 4.68 per 1,000,000 inhabitants), in women vs men (6.73 vs 3.90 per 1,000,000 inhabitants), and in patients with polyostotic FD or MAS vs those with monostotic FD (4.17 vs 1.19 per 1,000,000 inhabitants).
• The annual incidence of FD or MAS was 2.58 per 1,000,000 inhabitants in 2024, with higher incidences observed in children vs adults (4.02 vs 2.20 per 1,000,000 inhabitants), in women vs men (2.89 vs 2.25 per 1,000,000 inhabitants), and in patients with polyostotic FD or MAS vs monostotic FD (1.63 vs 0.95 per 1,000,000 inhabitants).
• For bone-related treatments, an average of 27% of patients per year received bisphosphonate therapy between 2020 and 2024; outpatient dispensing data showed that an average of 7.4% per year received phosphate supplements, 2.5% received denosumab, 0.4% received tocilizumab, and 0.2% received burosumab.
• Regarding endocrine treatments, an average of 3.3% of patients per year received aromatase inhibitors, 8.0% received pituitary treatments, and 2.2% received antithyroid agents.

IN PRACTICE:

"The implementation of outpatient diagnostic codes, associated diagnoses, and/or clinical data in national or European databases would allow for a more accurate estimation of the prevalence of FD-associated manifestations, while reducing the recruitment bias inherent to large reference centres," the authors wrote.

SOURCE:

This study was led by Lucie Levaillant, Department of Pediatric Endocrinology and Diabetology, University Hospital of Angers, Endo-ERN Center for Rare Endocrine Conditions, Angers, France. It was published online on May 20, 2026, in The Journal of Clinical Endocrinology & Metabolism.

LIMITATIONS:

The lack of coding for outpatient care may have led to an underestimation of both incidence and prevalence of FD or MAS, especially for monostotic and paucisymptomatic forms. The possibility of diagnostic misclassification could not be ruled out as codes for FD and MAS have not been validated in the French National Health Data System. Patients hospitalised in more than one region were assigned to the region of their first hospitalisation. 

DISCLOSURES:

This study was supported by research grants awarded to Lucie Levaillant from the Société Française d'Endocrinologie et Diabétologie Pédiatrique, the University Hospital of Angers, and other sources and by a grant to another author from the French Rare Disease Healthcare Network for Bone, Cartilage, and Calcium Disorders. The authors declared having no conflicts of interest.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.