Abstract
We confirmed homozygous type of relatively small expansion of CAG triplet repeats (57 repeats) in the short arm of chromosome 12 in a male patient with dentatorubral-pallidoluysian atrophy (DRPLA) by the polymerase chain reaction. He showed early onset (age 17yr) of DRPLA. His family history showed that his father and mother were first cousin, but neither showed any signs of DRPLA at the respective ages of 73 and 71. They had expanded 57 triplet repeats of the same size as the patient's but as a heterozygous state. Their normal alleles were 15 triplet repeats. There was good correlation of the age of onset with the number of triplet repeats in DRPLA. The homozygous state for the expansion of the triplet repeats was responsible for the early onset of his DRPLA
