Dentatorubropallidoluysian atrophy in Chinese

Background: Dentatorubropallidoluysian atrophy (DRPLA) is a rare, autosomal dominant neurodegenerative disease characterized by a range of clinical ma nifestations, including cerebellar ataxia, epilepsy, myoclonus, chorcoathet osis, and dementia. Outside the Japanese population, the prevalence is extr emely low worldwide. The reason for different ethnic prevalences of DRPLA i s unclear. A previous assumption was that large normal alleles contribute t o generation of expanded alleles and the relative frequencies of DRPLA. Objectives: To describe the clinical, radiological, and genetic features of the first reported Chinese family with DRPLA, to our knowledge, and to com pare the size distribution of normal alleles at the DRPLA locus in healthy Chinese individuals with that of other ethnic groups. Patients and Methods: Of 80 Chinese kindreds with autosomally dominant spin ocerebellar ataxias, 1 pedigree with 2 affected patients was found by polym erase chain reaction to carry the characteristic DRPLA mutation. The allele frequencies of different CAG repeat lengths at the DRPLA locus in 225 heal thy Chinese individuals were also analyzed and compared with Japanese, whit e, and African American distributions. Results: The clinical presentations of the 2 Chinese patients affected with DRPLA are similar to those described in japanese patients, except that the affected father exhibited myoclonus but not chorea. Although the normal DR PLA allele size is distributed similarly in Chinese and japanese population s, DRPLA, in Chinese individuals is rare. Thus far, to our knowledge, only 1 intermediate-sized allele containing more than 30 CAG repeats has been re ported among healthy Chinese individuals, in contrast to 3 among Japanese p opulations. Conclusion: The ethnic prevalence of DRPLA seems to be correlated with the prevalence of intermediate-sized alleles in individual populations.