Intergenerational instability and marked anticipation in SCA-17.

The authors describe an Italian family with autosomal dominant ataxia, dementia, psychiatric and extrapyramidal features, epilepsy, mild sensorimotor axonal neuropathy, and MRI findings of cerebral and cerebellar atrophy. A child had a distinctive presentation with onset at 3 years, growth retardation, fast progression, and early death. Molecular analysis demonstrated an expanded CAG/CAA repeat in the TBP gene (SCA-17). The repeat size was 66 triplets in the child and 53 in all the other patients.