The pathogenetic basis for a disease continuum in early- and late-onset ataxia-dystonia supports a unified genetic diagnostic approach

•Anatomical damage to the cortico-basal-ganglia-pontocerebellar network is associated with comorbid dystonia in both EOA and LOA gene groups.•EOA, LOA and mixed ataxia-dystonia gene groups share biological pathways of brain development, neural signaling, and cellular processes.•The clinical classification into EOA and LOA is not reflected by different gene expression patterns before or after 25 years of age.•Our findings in EOA, LOA and mixed ataxia-dystonia point to a shared disease continuum.•Our findings question the clinical relevance of classifying and diagnosing ataxia as separate EOA, LOA and/or comorbid dystonia disease groups.