RESUMO
Objective To investigate the clinical features and the gene mutation of patients with spinocerebellar ataxia type3 and type7.Methods The trinucleotide repeat mutations were detected by polymerase chain reaction (PCR),agarose gel electrophoresis method,and DNA sequencing in 13 patients,4 related members and 4 common members from 3 spinocerebellar ataxia families.Results Among the 13 patients,four patients had SCA3/MJD(CAG) n expansion mutation(n = 65 ～ 74),nine patients had SCA7 allele expansion for 40 ～ 52 times.Patients with type 3 or 7 showed significant difference in nervous system injury.Conclusion The difference of clinical feature might be used in diagnosis of SCA3/MJD and SCA7,but genotype determination would be the only method of definite diagnosis.