Crystalline encephalopathy: cerebral immunoprotein deposits and isolated angiitis.

Brain biopsy specimens from a 38-year-old woman with adversive seizures and bifrontal mass lesions evident on computed tomographic scans showed extracellular and intracellular deposits of crystallized proteins. These were morphologically identical to the immunoglobulin crystals seen in reactive or neoplastic plasma cells and by peroxidase-antiperoxidase methods were found to contain polyclonal immunoglobulins. In addition, severe angiitis of the intracerebral blood vessels was present.