SAT-731 - Mccune Albright Syndrome: Real World Evidence in Clinical Practice.

Introduction: McCune–Albright syndrome (MAS) is a rare sporadic disorder characterized by fibrous dysplasia, café-au-lait skin pigmentation, and endocrine hyperfunction. Skeletal involvement may progress leading to deformities, fractures, chronic pain, and significant morbidity in adulthood.
Herein, we report three adult cases from Argentina illustrating the clinical heterogeneity and longterm burden of MAS.

Objective: report clinical cases highlighting skeletal involvement and disease-related complications.

Case 1. A 44-year-old woman with MAS, diagnosed in the presence of café-au-lait skin pigmentation, fibrous dysplasia, and a history of precocious puberty and hyperthyroidism. She showed radiological progression of fibrous dysplasia. At evaluation, she presented inflammatory polyarthritis and was diagnosed with seropositive rheumatoid arthritis. Imaging revealed extensive craniofacial fibrous dysplasia with middle and inner ear involvement. Laboratory evaluation showed increased FGF23 levels. Treatment with intravenous zoledronic acid was initiated.

Case 2. A 21-year-old woman with polyostotic MAS, diagnosed in early childhood due to peripheral precocious puberty treated with GnRH analogs. She sustained rib fractures requiring surgical resection and prosthetic reconstruction, with histological confirmation of fibrous dysplasia. Imaging
showed extensive skeletal involvement, including ribs, spine, pelvis, and hips, with an expansive lytic iliac lesion and soft tissue extension. She is currently managed with intravenous pamidronate and analgesics for chronic pain, under multidisciplinary follow-up with significant impact on quality of life.

Case 3. A 40-year-old woman with long-standing polyostotic MAS, diagnosed after precocious puberty and confirmed by bone biopsy in adolescence. She presents extensive skeletal involvement, chronic disabling bone pain without history of fractures. Imaging revealed marked craniofacial involvement and widespread uptake on bone scintigraphy. She has associated endocrinopathies, including hypothyroidism. Despite prolonged intermittent oral bisphosphonate therapy, pain and biochemical activity persist, with limited access to advanced antiresorptive treatments, resulting in significant impairment of quality of life.

Conclusion: These three cases illustrate the marked clinical heterogeneity of McCuneAlbright syndrome in adults, with variable skeletal burden, endocrine involvement, and impact on quality of life. A multidisciplinary approach and individualized long-term follow-up are essential to optimize
outcomes in this rare disorder.

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