[A family with dentato-rubro-pallido-luysian atrophy (DRPLA): an intergenerational contraction of the CAG repeat].

: We describe the relation of the CAG repeat length to the genetic anticipation in a Japanese family with dentato-rubro-pallido-luysian atrophy (DRPLA). The proband, a 21-year-old woman, developed epilepsy at age 19. Her mother has displayed cerebellar ataxia, choreoathetosis, and dementia since age 40, and the grandmother has shown cerebellar ataxia since age 52. So a genetic anticipation was observed. The CAG repeat sizes of peripheral blood lymphocytes from the proband, mother, and grandmother were found to be 61, 59, and 60, respectively. Thus, the mother showed earlier onset but a smaller CAG repeat length as compared to the grandmother. This case is thought to be rare and valuable in respect that the intergenerational contraction of the CAG repeat was shown in spite of the genetic anticipation was observed.