Argyrophilic glial intracytoplasmic inclusions in multiple system atrophy: immunocytochemical and ultrastructural study.

Argyrophilic intracytoplasmic inclusions in oligodendrocytes (AGCIs) were seen in all of 15 cases of multiple system atrophy (MSA), and none in other neurodegenerative diseases, including 9 cases of Menzel-type olivopontocerebellar atrophy and 4 cases of Joseph's disease. The inclusions were widespread, not only in the olivopontocerebellar and striatonigral systems but also among fibers connecting their affecting lesions of MSA. Immunohistochemically, they were closely associated with tau, tubulins and microtubule-associated protein 5. Ultrastructurally, they consisted of 30- to 50-nm filaments (not tubules) and electron-dense granules, in varying proportions, and their formation is discussed. The specific occurrence of AGCIs could be a key to approach the pathogenesis of MSA.