Table 1.
Characteristics of the Polyglutamine Diseases
| Repeat Disorder | Gene | Prevalence | Variance in AAO Explained by Repeat Length | Normal Range | Pathogenic Range | Somatic Instability |
|---|---|---|---|---|---|---|
| HD | HTT | 3–10 | 50–60% (40–60%) | 6–35 | 40–121 | Yes |
| SCA1 | ATXN1 | 0.16 | 64–76% (no detected heritable component) | 6–38 | 45–83 | Yes |
| SCA2 | ATXN2 | 0.2 | 50–80% (17–59%) | 15–31 | 33–500 | Yes |
| SCA3 | ATXN3 | 0.4 | 45–80% (46%) | 12–44 | 52–87 | Yes |
| SCA6 | CACNA1A | 0.04 | 26–52% (no detected heritable component) | 4–18 | 20–33 | Unknown |
| SCA7 | ATXN7 | 0.12 | 71–88% (no detected heritable component) | 3–19 | 37–460 | Yes |
| SCA17 | TBP | <0.02 | Unknown | 25–40 | 49–66 | Unknown |
| DRPLA | ATN1 | 0.005–0.04 | 50–68% | 6–35 | 48–93 | Yes |
| SBMA | AR | 0.65–2.00 | 29% | 9–34 | 38–72 | Yes |
Epidemiology and CAG repeat ranges of polyglutamine diseases. Prevalence is given/100,000 European population. AAO = age at onset; HD = Huntington's disease; SCA = spinocerebellar ataxia; DRPLA = dentatorubral‐pallidoluysian atrophy; SBMA = spinal and bulbar muscular atrophy.