Minimum prevalence of spinocerebellar ataxia 17 in the north east of England.

OBJECTIVE

To determine the minimum prevalence of spinocerebellar ataxia type 17 (SCA17) in the north east of England.

PATIENTS AND METHODS

A defined region containing 2,516,500 individuals with 192 families with undiagnosed ataxia, 90 patients with a Huntington's disease-like phenotype and 292 controls. The number of (CAG/CAA)(n) repeats in the SCA17/TBP gene was determined by fluorescent PCR and sequenced in affected individuals.

RESULTS

The mean repeat size for 584 control alleles was 34 (S.D.=3.58), ranging from 25 to 40. Two index cases had larger alleles with repeat lengths greater than the control range. Affected family members presented in adult life with ataxia followed by extrapyramidal features and cognitive impairment. In one family 44 repeats were associated with a younger age of onset than has been previously described.

CONCLUSIONS

The minimum prevalence of SCA17 in the north east of England was 0.16/100,000 (upper 95% confidence interval 0.31/100,000).