| Combined prevalence | Approximately 1–5 per 100,000 worldwide, though rates vary significantly by region and ethnicity |
| SCA3 (Machado-Joseph disease) | The most common SCA globally, particularly prevalent in Portugal, Brazil, Japan, and China. Accounts for approximately 21–36% of all SCA cases |
| SCA2 | Second most common worldwide; particularly prevalent in Cuba (40 per 100,000 in Holguín Province, the world's highest known concentration) |
| SCA1 | Third most common; relatively uniform distribution |
| SCA6 | More common in Japan and older-onset populations; accounts for 13–15% of dominant ataxias in Japan |
| SCA7 | Rare in most populations but relatively common in parts of South Africa and Scandinavia |
| Age of onset | Most subtypes present between ages 20–50, though childhood and late-onset forms occur. Earlier onset generally correlates with larger repeat expansion sizes (genetic anticipation) |
| SCA5 | Missense mutations in SPTBN2 (β-III spectrin), disrupting Purkinje cell dendritic architecture |
| SCA14 | Mutations in PRKCG (protein kinase C γ), causing aberrant signaling |
| SCA27 | Mutations in FGF14, disrupting voltage-gated sodium channel function |
| SCA28 | Mutations in AFG3L2, causing mitochondrial protease dysfunction |
| High metabolic demand | Purkinje cells are among the largest and most metabolically active neurons in the brain |
| Databases | OMIMOrphanetClinicalTrialsPubMed |