Unusual Presentation of Fibrous Dysplasia in an Elderly Patient.

Fibrous Dysplasia is a benign fibro-osseous lesion occurring throughout the skeletal system with a predilection for craniofacial bones, long bones, and ribs. Fibrous dysplasia develops during bone formation and growth with a variable natural evolution. It is considered a genetic nonheritable disease resulting from missense mutations that occur postzygotically in the GNAS1 gene. This mutation leads to a focal congenital failure of proper bone formation and arrest at the woven bone stage. In turn, this leads to a decreased mechanical strength, causing bone pain, pathological fractures, and skeletal deformities. Besides clinical examination, fibrous dysplasia is diagnosed based on the results of radiographic imaging and the microscopic histopathological findings. On CT scan, fibrous dysplasia shows the characteristic "Ground-glass" appearance with well-defined borders. On MRI, fibrous dysplasia has a low signal intensity on T1-weighted MRI and variable signal intensity on T2-weighted MRI. We hereby report a case of an unusual presentation of fibrous dysplasia in a 67-year-old female presenting to the emergency department with generalized malaise and lower limb pain. Fibrous dysplasia may present in the elderly population and can be difficult to differentiate from other malignant and benign lesions affecting the skeletal system.