Dentatorubropallidoluysian atrophy (DRPLA) is an autosomal dominant neurodegenerative disorder characterized by a variable combination of progressive ataxia, epilepsy, myoclonus, choreoathetosis and dementia. This disease is caused by a (CAG)(n) expansion in the DRPLA gene, on chromosome 12p13. DRPLA is prevalent in Japan, but several families of non-Japanese ancestry have already been published. To identify the origin of expanded alleles in Portuguese families with DRPLA, we studied two previously reported intragenic SNPs in introns 1 and 3, in addition to the CAG repeat of the DRPLA gene. The results showed that all four Portuguese DRPLA families shared the same haplotype, which is also common to that reported for Japanese DRPLA chromosomes. This haplotype is also the most frequent in Japanese normal alleles, whereas it was rare in Portuguese control chromosomes. Thus, our findings support that a founder DRPLA haplotype of Asian origin was introduced in Portugal, being responsible for the frequency of the disease in this country.