RFC1 and sensory ataxia: Cerebellar Ataxia Neuropathy Vestibular Areflexia Sindrome (CANVAS) is a late onset familial or sporadic form of sensory ataxia caused by recessive biallelic pentanucleotide repeat expansion (AAGGG) in the RFC1 gene which encodes the large subunit of replication factor C (RFC), a heteropentameric AAA+ protein complex associated with DNA synthesis during replication and repair.