Table 2
Autosomal dominant cerebellar ataxia. Only those for which gene tests are currently available are listed
| ADCA type | Clinical features | Genetic loci and chromosomal location | Normal allele (repeats) | Pathological allele (repeats) |
|---|---|---|---|---|
| Despite the clinical classification most labs will simply do all the SCAs (1, 2, 3, 6, and 7) in one batch. | ||||
| SCAs 12 and 17 are extremely rare and are not usually tested as a routine. | ||||
| ADCA I | Cerebellar syndrome plus: | SCA 1 6p22-23 | 6-44 | 39-83 |
| –pyramidal signs | SCA 2 12q23-24.1 | 13-33 | 32-77 | |
| –supranuclear ophthalmoplegia | SCA 3 14q32.1 | 12-40 | 54-89 | |
| –extrapyramidal signs | SCA12 5q31-33 | 22-30 | 66-78 | |
| –peripheral neuropathy | SCA 17 6q27 | 25-42 | 47-63 | |
| –dementia | ||||
| ADCA II | Cerebellar syndrome plus: | SCA 7 3p12-21.1 | 4-35 | 36-306 |
| –pigmentary maculopathy | ||||
| –other signs as ADCA I | ||||
| ADCA III | “Pure” cerebellar syndrome | SCA 6 19p13 | 4-18 | 20-33 |
| Mild pyramidal signs | ||||
