Mutations in DnaJC29 (sacsin), a 521 kDa J protein, cause early-childhood-onset (age 1–2 years), recessive spastic ataxia of Charlevoix-Saguenay (ARSACS; Bouchard et al., 1978). Here, SACS is linked to Autosomal recessive spastic ataxia of Charlevoix-Saguenay.