[Advances in understanding of clinical presentations and molecular mechanisms of triplet repeat diseases].

Triplet repeat diseases are diseases caused by unstable expansion of trinucleotide repeats in the causative genes. Identification of the causative genes has made it possible to understand the clinical presentations and molecular mechanisms of neurodegeneration caused by expanded triplet repeat diseases. In the triplet repeat diseases caused by expansion of CAG trinucleotide repeats, the CAG repeats code for polyglutamine stretches. Evidences, which indicate that proteins with expanded polyglutamine stretches result in aggregate formation and induce apoptosis, are accumulating, and it is expected that development of therapeutic measures for triplet repeat diseases will become a reality in the near future.