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. 2024 May 17;109(6):1423-1432.
doi: 10.1210/clinem/dgad744.

Incidence and Prevalence of Fibrous Dysplasia/McCune-Albright Syndrome: A Nationwide Registry-Based Study in Denmark

Maartje E Meier  1 , Emese Vágó  2 , Bo Abrahamsen  3   4 , Olaf M Dekkers  2   5   6 , Erzsébet Horváth-Puhó  2 , Lars Rejnmark  7 , Natasha M Appelman-Dijkstra  6
Affiliations

Incidence and Prevalence of Fibrous Dysplasia/McCune-Albright Syndrome: A Nationwide Registry-Based Study in Denmark

Maartje E Meier et al. J Clin Endocrinol Metab. .

Abstract

Context: Fibrous dysplasia/McCune-Albright syndrome (FD/MAS) is a rare genetic disorder. Incidence and prevalence are not well-studied. Epidemiological research is complicated by the rarity of FD/MAS, absence of registries, heterogeneous presentation, and possibly asymptomatic phenotype. FD/MAS may present with FGF23-mediated hypophosphatemia, of which the epidemiology is also unclear.

Objective: Evaluate incidence and prevalence of FD/MAS and FD/MAS-related hypophosphatemia.

Methods: This cohort study based on the nationwide Danish National Patient Registry from 1995-2018, included patients identified by ICD-10 codes M85.0 (monostotic FD [MFD]) and Q78.1 (polyostotic FD [PFD]/MAS). Incidence rates and prevalence were calculated and stratified by sex, age, calendar period, and diagnosis code. Cases were screened for FD-associated hypophosphatemia by diagnosis code E.83 (disorder of mineral metabolism) and dispatched vitamin D analogues.

Results: A total of 408 patients were identified, 269 with MFD (66%), 139 with PFD/MAS (34%), comparable between sexes. Incidence of FD/MAS demonstrated increasing secular trend with a rate of 3.6 per 1 000 000 person-years (95% CI: 2.9, 4.5) in 2015-2018. Incidence peaked between age 11 and 20. Prevalence of FD/MAS increased over time to 61.0 (95% CI: 54.6, 67.4) per 1 000 000 persons in 2018. The incidence rate of MFD was 1.5-fold that of PFD/MAS in the first decade, rising to 2.5-fold in the last decade. No FD/MAS cases were registered with diagnosis code or treatment for hypophosphatemia.

Conclusion: FD/MAS is rare, diagnosis peaks during adolescence without sex predominance, and MFD is most prevalent. Hypophosphatemia may be underdiagnosed and undertreated, or it may be underregistered, comparing this study to literature.

Keywords: epidemiology; fibrous dysplasia/McCune-Albright syndrome; incidence; prevalence; rare bone disorder; registry.

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Figures

Figure 1.
Figure 1.
Incidence by calendar period and sex.
Figure 2.
Figure 2.
Incidence by age and calendar period.
Figure 3.
Figure 3.
Incidence by calendar period and ICD.
Figure 4.
Figure 4.
Incidence by age and ICD.
Figure 5.
Figure 5.
Prevalence by age and calendar year.
Figure 6.
Figure 6.
Prevalence by age and sex in 2018.
Figure 7.
Figure 7.
Year of incidence by birth year for all age groups. The blue area indicates the birth year and year of incidence range for each age group separately. For example, FD/MAS cases belonging to age group 11 to 20 in 2018 were born between 1998 and 2008 and were incident between 1998 and 2018. The total blue bar represents the total of the patients with FD/MAS in the age group. The red line marks the year 1994, where the ICD coding changed from the ninth to the tenth revision. The dark blue component of the bar represents the patients actually diagnosed in the ICD-10 coding system and included in this study. The light blue component represents the patients with FD/MAS coded by ICD-9 before 1994. These patients are missed in the current study if they were not reportedly diagnosed in the ICD-10 system. The chart reflects that in older age groups, higher ratios of cases are missed in this study, that is, the underestimation is higher for older age groups.
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References

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