Autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS) has been described in the Quebec region and in Tunisia. We report on two Japanese siblings with a new homozygous mutation (6543 del A) of the SACS gene. Compared with previously reported ARSACS patients, both of these patients had a unique phenotype characterized by dementia, ophthalmoplegia, and the absence of prominent retinal myelinated fibers. (c) 2004 Movement Disorder Society.