We describe a 39-year-old Japanese woman with familial amyotrophic lateral sclerosis (FALS) in whom we identified a missense mutation (Gly93-->Ser) in exon 4 of the Cu/Zn superoxidase dismutase-1 (SOD1) gene in which no pathological data have been available. The disease duration was 16 years, and she died of respiratory failure. The initial sign was weakness of the lower limbs. She had no clear upper motor neuron involvement. Respiratory muscle weakness had developed 1 year before her death. Neuropathological examinations showed simultaneous involvement of the pyramidal tract and lower motor neurons as well as degeneration in the Clarke's nucleus, the spinocerebellar tract, the posterior column, the dentatorubral system, and anterolateral columns of the spinal cord. However, the patient has no Lewy body-like hyaline inclusions (LBHIs), which are characteristic features of mutant SOD1-related FALS with posterior column involvement. Based on clinical, genetic and pathological findings with a review of the literature, we suggest that degeneration of the dentatorubral system and the absence of LBHIs in our case are pathological features in FALS with the Gly93Ser mutation.