Intracytoplasmic inclusions (Bunina bodies) in amyotrophic lateral sclerosis

In an autopsy case of sporadic amyotrophic lateral sclerosis, there were intracytoplasmic eosinophilic inclusions of the Bunina type in motor neurons. Electron microscopically, these bodies were observed as amorphous substances, irregularly deposited around the endoplasmic reticulum to form masses. Similar small masses were also visible in mitochondria. These substances did not stain for acid phosphatase. By analytical electron microscopy they contained silicon. Bunina bodies, therefore, seem to be due to deposition of some metabolite, but their nature is still obscure.