A Rare Case of Radiculopathy: Monostotic Fibrous Dysplasia of the Sacrum.

Fibrous dysplasia is a bone disease characterized by an osteoblastic dysfunction resulting in a fibrous replacement of the normal medullary bone. We describe the case of a 33-year-old who presented with low back pain irradiating to her right leg. Both the computed tomography scan and magnetic resonance imaging showed an osteolytic, multicystic lesion of the right hemi-sacrum with invasion of the right S1 foramen. She underwent foraminotomy and curettage of the lesion. Histological diagnosis was fibrous dysplasia, without features of malignant transformation. Three years after surgery the patient is asymptomatic and imaging is stable. This is the fifth known case of monostotic fibrous dysplasia involving the sacrum, a rare entity that must be considered in the differential diagnosis when approaching patients with sacral lesions.