SUN-738 Clinical Characteristics Of Fibrous Dysplasia And Mccune-albright Syndrome: A Retrospective Study At The University Of Miami

Abstract Disclosure: R.R. Savian: None. L. Zheng: None. R.J. Galindo: None. G. Arevalo: None. J. Paris: None. V.S. Lagari-Libhaber: None. Background: Fibrous dysplasia (FD) is a rare mosaic skeletal disorder characterized by replacement of normal bone with fibro-osseous tissue. It presents as monostotic or polyostotic disease and may co-occur with hyperfunctioning endocrinopathies and café-au-lait macules in McCune-Albright syndrome (MAS). Despite established guidelines, longitudinal data on clinical outcomes and specialty follow-up in adult FD populations remain limited. Methods: We conducted a retrospective review of adults with FD evaluated at the University of Miami, a tertiary referral center, between 2014 and 2024. Of 540 patients initially identified by ICD coding, 102 were included based on availability of complete and verifiable clinical data. The cohort included a large number of Hispanic patients, offering unique insight into the burden of a rare skeletal disorder in an underrepresented population. Disease subtype, endocrine manifestations, skeletal complications, biochemical profiles, treatment approaches, and specialty follow-up were assessed. Results: Among 102 patients (mean age 50.1 ± 18.7 years), 62.7% were female. Polyostotic FD was present in 56.9%, monostotic in 43.1%. MAS was diagnosed in 15.7%, with associated endocrinopathies: precocious puberty (4.9%), growth hormone excess (2.9%), cortisol excess (2.9%), and hypophosphatemia (5.9%). Café-au-lait macules were observed in 15.7%. Chronic bone pain was reported by 74.5% of patients, and fractures occurred in 38.2%, with 24.5% experiencing pathologic fractures attributable to FD. Osteoporosis was noted in 25.5%. ALP levels were significantly higher in MAS vs. non-MAS (275.5 vs. 95.7 U/L, p = 0.027). Vitamin D was significantly lower in monostotic vs. polyostotic FD (22.3 vs. 31.4 ng/mL, p = 0.041), although not associated with fracture risk. Differences in fracture rates by disease type, sex, MAS, or hypophosphatemia were not statistically significant. Bone-targeted therapy was used in 27.5%—primarily IV zoledronic acid or oral bisphosphonates—with reported pain improvement in 70% of IV-treated vs. 61.1% of oral-treated patients; this difference did not reach statistical significance. Only 41.1% of patients were evaluated by endocrinology despite documented endocrine comorbidities. Conclusion: Adults with FD/MAS experience a high burden of skeletal fragility, chronic pain, and metabolic complications. Biochemical differences by disease subtype—such as elevated ALP in MAS and lower vitamin D in monostotic FD—may reflect distinct underlying disease biology. Although no statistically significant predictors of fracture were identified, observed trends support the need for larger, prospective studies. The low rate of endocrine specialty follow-up—despite frequent hormonal involvement—underscores an opportunity to improve multidisciplinary care and long-term outcomes in this population. Presentation: Sunday, July 13, 2025