Dear Editor,
Huntington's disease (HD) is an autosomal dominant neurodegenerative disease characterized by movement disorder, progressive dementia, and psychiatric and behavioral changes.It is caused by unstable expanded CAG trinucleotide repeats in exon 1 of the huntingtin (HTT)gene, located on chromosome 4p16.3 [1].The number of CAG repeats is inversely correlated with the onset age of HD, with more expanded CAG repeats correlated with an earlier onset [2].In previous studies, we have confirmed the inverse correlation between the onset age and the CAG repeat size in Chinese HD patients [3, 4].