An Unusual Case of Polyostotic Fibrous Dysplasia in a 53-Year-Old Woman With Low Back Pain

ObjectiveThe purpose of this case report is to describe the features of an unusual presentation of fibrous dysplasia.Clinical FeaturesA 53-year-old woman had low back pain and numbness in the anterior upper left thigh that started 3 years earlier after a fall. She experienced pain during active lumbar flexion and extension range of motion. Radiographic examination demonstrated an oval geographic osteolytic lesion in the left ilium and abnormal trabecular architecture with variable-sized osteolytic lesions and both ill-defined and well-defined borders along the sacroiliac joint margin.Intervention and OutcomeBecause of the aggressive osteolytic appearance, magnetic resonance imaging of the pelvis with gadolinium contrast was obtained for additional characterization of the lesions. There were 3 additional mixed signal lesions located within the left femoral neck and extending to the greater trochanter that enhanced with contrast. Because of the suspicion of malignancy, needle biopsy was performed. The pathologic findings in combination with the radiographic appearance confirmed the diagnosis of polyostotic fibrous dysplasia.ConclusionThis case demonstrated a rare aggressive appearance of polyostotic fibrous dysplasia located in the left innominate and the left proximal femur that prompted a diagnostic imaging workup and biopsy for suspected skeletal malignancy. These lesions may require careful evaluation by an experienced team of physicians, radiologists, and pathologists to ensure proper diagnosis and treatment.