In this review, we focus on the most prevalent and clinically relevant subgroups affecting adults that clinicians may find in their clinical practice: spinocerebellar ataxias (SCA1, SCA2, SCA3, SCA6, SCA7, SCA17, SCA27B), dentatorubral–pallidoluysian atrophy (DRPLA), Friedreich’s ataxia (FRDA), cerebellar ataxia with neuropathy and vestibular areflexia syndrome (CANVAS), spastic paraplegia type 7 (SPG7) and fragile X-associated tremor/ataxia syndrome (FXTAS) [1]. The gene discussed is ATXN3; the disease is fragile X-associated tremor/ataxia syndrome.