Gun ZH, Osamor C, Taylor J, Li X, Szymczuk V, Boyce AM. Serum Phosphorus as a Driver of Skeletal Morbidity in Fibrous Dysplasia.
J Clin Endocrinol Metab 2024;
109:1334-1340. [PMID:
37975816 PMCID:
PMC11031212 DOI:
10.1210/clinem/dgad671]
[Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/30/2023] [Revised: 09/19/2023] [Accepted: 11/13/2023] [Indexed: 11/19/2023]
Abstract
CONTEXT
Fibrous dysplasia (FD) results in fractures, pain, and deformities. Abnormal osteoprogenitor cells overproduce FGF23, leading to hyperphosphaturia in most patients and frank hypophosphatemia in a subset. Studies suggest hypophosphatemia is associated with increased FD-related morbidity. However, the relationship between phosphorus and skeletal complications has not been investigated, and the optimal therapeutic target has not been determined.
OBJECTIVE
Characterize the impact of serum phosphorus on FD-related morbidity and identify levels associated with increased skeletal complications.
METHODS
Natural history study with 240 subjects at a clinical research center who had ≥1 fasting phosphorus level, determined as age- and sex-adjusted Z-scores. Subjects were categorized based on frank hypophosphatemia (Z-score ≤ -2; n = 48); low-normophosphatemia (> -2 to ≤ -1; n = 66); and high-normophosphatemia (> -1 to ≤ 2; n = 125). Main outcomes were fractures, orthopedic surgeries, and scoliosis.
RESULTS
Subjects with frank and low-normophosphatemia had increased fracture and surgery rates vs high-normophosphatemia. The prevalence of moderate to severe scoliosis was similarly higher in the frank and low-normophosphatemia groups. In a subanalysis of patients matched for Skeletal Burden Score ≥35, fracture and surgery rates remained higher in the frank hypophosphatemia group, suggesting association between phosphorus and skeletal complications is not explained by differences in FD burden alone.
CONCLUSION
Both frank hypophosphatemia and low-normophosphatemia are associated with increased FD-related complications. This supports FGF23-mediated hypophosphatemia as a driver of skeletal morbidity, which may impact a larger proportion of the FD/McCune-Albright syndrome population than previously recognized. These findings enable clinicians to identify at-risk patients and will inform development of prospective studies to determine optimal therapeutic targets.
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