Introduction: Fibrous dysplasia (FD) is a typically benign condition whereby normal bone is progressively replaced by fibrous tissue and irregular bony trabeculae. Mutations of the GNAS1 gene on chromosome 20, which develop sporadically during early pregnancy, are responsible for the development of FD and lead to abnormal differentiation of osteoblasts, contributing to the formation of fibro-osseous tissue. Fibrous dysplasia most commonly affects the craniofacial region, with 90% of cases presenting before age five.Case Report: This case study follows the history and diagnosis of a 13-year-old patient who presented to East Lancashire Hospital Trust’s Emergency Department with a two-year history of on-and-off swelling to the left side of her face. After multiple investigations, including imaging and biopsies, she was diagnosed with FD.Conclusion: This case highlights the diagnostic challenges associated with FD, particularly when presenting with overlapping signs of common odontogenic pathologies.In this 13-year-old patient, recurrent facial swelling, trismus, and radiographic abnormalities initially suggested dental cysts or keratocysts. However, advanced imaging and histological correlation ultimately led to the diagnosis of FD.
