The phenotype associated with the replication factor C subunit 1 gene (RFC1) expansion is broadening to include Parkinsonism especially when multiple systems atrophy (MSA) is suspected.

In 2019, a recessive pentanucleotide intronic repeat expansion in the RFC1 gene was identified as the cause of the late-onset neurodegenerative disease cerebellar ataxia, neuropathy, vestibular areflexia syndrome (CANVAS).1 Subsequent detailed genotype/phenotype studies have confirmed the main phenotype as a large fibre sensory ataxic neuropathy with cerebellar and vestibular involvement with onset usually from the fifth decade. A preceding chronic cough is common and other features include autonomic involvement and occasionally brisk reflexes. In the paper by Sullivan et al, the authors report the RFC1 expansion in three patients with cerebellar ataxia, parkinsonism and autonomic dysfunction (and neuropathy in 2/3) out of a total of 207 …