Monostotic fibrous dysplasia of the lumbar spine.

Monostotic fibrous dysplasia is exceedingly rare. We report a case in a 61-year-old woman with a history of recurrent low back pain and sciatica since 35 years of age. While walking, she suddenly experienced pain in her right thigh. The pain spread gradually to the buttock and calf on the same side, becoming increasingly severe. The time pattern was mechanical, with exacerbation during straining. Paresthesia developed over the dorsal aspect of the right foot. Nonsteroidal antiinflammatory drugs were ineffective. Radiographs of the spine showed an expansile and heterogeneous lesion in the body of L2. Hyperactivity of L3 and L4 was seen on the bone scan. Computed tomography demonstrated heterogeneity of L2, L3, and L4, as well as hypertrophy of the neural arch of L3 and of the right posterior lamina and spinous process of L4. Alterations in L2, L3, and L4 were noted on the magnetic resonance imaging study, which showed no evidence of epidural involvement. Laboratory tests were normal. A surgical biopsy of L3 established the diagnosis of fibrous dysplasia. Since the seminal description of fibrous dysplasia in 1891, only 21 cases of monostotic spinal involvement have been published. The spinal lesions can remain clinically silent or cause spinal pain with or without neurological symptoms. Radiographic findings are variable (heterogeneity, osteolysis, expansion without cortical violation or soft tissue involvement). Calcium and phosphate levels are normal. The diagnosis depends on examination of a vertebral biopsy specimen.