This report concerns an autopsy case of amyotrophic lateral sclerosis (ALS) with unusual clinical and neuropathological findings. The patient was a Japanese man without hereditary burden who was 49 years old at the time of death. His clinical manifestation included dysarthria at age 48, followed by dysphagia, atrophy and fasciculation of the tongue, muscle weakness in the four extremities, tremor, rigidity, increased deep tendon reflexes in the upper and lower extremities, and incoordination of the four extremities. He died of respiratory failure 12 months after the disease onset. No respirator administration was performed throughout the clinical course. The neuropathological examination revealed not only degeneration of upper and lower motor neuron systems, including the presence of Bunina bodies and ubiquitin-immunoreactive neuronal inclusions in the lower motor neurons, but also prominent degeneration of the substantia nigra and dentate nucleus with slight neuronal loss in the locus ceruleus and pontine nucleus. To our knowledge, this is the first reported case of sporadic ALS without dementia and respirator support, showing degeneration of the substantia nigra and dentate nucleus. This report may contribute to the resolution of the question concerning the neuropathological heterogeneity of sporadic ALS with respiratory support.