Autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS) was originally found among the inhabitants of the Charlevoix-Saguenay region of Quebec, Canada. This disease is characterized by early-onset ataxia, spasticity, peripheral neuropathy, finger and foot deformities, and hypermyelination of the retinal nerve fibers. The mentality of the patients is usually intact. The principal neuropathology comprises atrophy of the upper vermis and the loss of Purkinje cells in the cerebellum. Although the lateral corticospinal tracts are degenerated, the precentral gyrus, dentate nucleus, and inferior olivary nucleus are intact. Recently, the gene responsible for ARSACS was determined to encode the sacsin protein in the Quebec patients. In 2004, we first reported a Japanese family with a SACS mutation. So far, we have identified the SACS mutations in a total of five Japanese families with ARSACS and analyzed the clinical features of eight patients. Interestingly, we found some atypical clinical features in the Japanese patients: a slightly later onset than that of the Quebec patients, an absence of myelinated retinal fibers, intellectual impairment, and a lack of spasticity. To date, there have been descriptions of non-Quebec patients with SACS mutations in Japan, Italy, Tunisia, and Turkey. Hereafter, as more SACS mutations are identified, the clinical spectrum of the "sacsinopathies" could expand.