Clinical features and genetic analysis of a Spanish family with spinocerebellar ataxia 6.

Objective - To present the clinical features and DNA analysis of a Spanish SCA6 family. Material and methods - Four symptomatic members of the family (mean age at onset: 53.75 ± 5.21) were examined. SCA6 CAG trinucleotide repeat was analysed in the proband by the polymerase chain reaction (PCR). Results - Early dysphagia, ophthalmoparesis and neck dystonia in the oldest patient, without the loss of vibratory and proprioceptive sensation supporting the theory of phenotypic variability within families with SCA6. Our results are in accordance with the theory that the size of the repeat pattern correlates with the age at onset of the symptoms. Analysis of the SCA6 CAG trinucleotide repeat at the CACNA1A gene in the patient's DNA demonstrated an expanded allele of 22 CAG repeat units. Conclusions - This study identifies phenotypic differences in the surviving kindred. The diagnosis of SCA6 in family members or single affected patients can be made by direct molecular analysis. This makes predictive testing possible.