Further postmortem examination of a case of familial ataxia with cerebrospinal fluid abnormality: an electron microscopic study of the intracytoplasmic eosinophilic inclusion bodies in the central nervous system.

As reported previously, the peculiar intracytoplasmic eosinophilic inclusion bodies (IEIBs) extensively appeared in the autopsied brain tissue from a 49-year-old man having familial ataxia with cerebrospinal fluid abnormality, and histochemically showed abundant proteins, but few lipids and carbohydrates. Ultrastructurally, many membrane-bound vacuoles derived from the distended cisterns of rough-surfaced endoplasmic reticulum (RER) appeared in the neurons. They were filled with fine granular, less dense materials. The IEIBs, shown as a homogeneous dense core, were found in some of the vacuoles. Similar vacuoles also appeared in astrocytes, oligodendrocytes, vascular pericytes, ependymal and choroidal epithelial cells. It is suggested that the vacuoles result from the accumulation of metabolic products in the distended RER cisterns of the cells in the central nervous system, presumably representing a genetically determined functional abnormality of the RER in protein synthesis and/or transport.