RFC1 and Rare hereditary ataxia: Recent additions to the list of genetically defined hereditary ataxias include two repeat-expansion disorders that were detected through NGS: intronic biallelic complex pentanucleotide RFC1 expansions causing cerebellar ataxia, neuropathy, and vestibular areflexia syndrome (CANVAS [MIM: 614575])1 and deep intronic monoallelic trinucleotide FGF14 expansions causing late-onset spinocerebellar ataxia 27B (MIM: 620174).2