Delayed Diagnosis of McCune-Albright Syndrome in Adulthood Revealed by Spinal Fibrous Dysplasia: Report of 2 Cases

McCune-Albright syndrome (MAS) is a rare genetic disorder characterized by fibrous dysplasia of bone, café-au-lait skin pigmentation, and endocrine abnormalities. Adult presentation with spinal fibrous dysplasia, although previously reported, is uncommon and diagnostically challenging. We report 2 cases of MAS diagnosed in young women who initially presented with persistent back pain. Both patients underwent imaging studies that revealed multiple lytic lesions in the spine, raising concern for metastatic disease. Further evaluation confirmed the presence of polyostotic fibrous dysplasia without evidence of malignancy. Both patients had a history of precocious puberty, consistent with the syndrome's known manifestations. In 1 case, the diagnosis was supported by detection of a somatic <i>GNAS</i> variant using next-generation sequencing on DNA and RNA extracted from bone biopsy. The second patient declined genetic testing. These cases highlight the importance of considering MAS in the differential diagnosis of spinal lesions in young individuals, particularly when imaging reveals multifocal, expansile, and radiolucent bone lesions. Early recognition is essential for appropriate management, genetic counseling, and monitoring of potential endocrine complications.