The frequency of polyQ diseases is ~1-10 cases per 100,000 people. HD and SCA3 have the highest occurrence worldwide. DRPLA predominantly takes place in Japan 33 , while SBMA has been reported with a high frequency in Finland. Although each disease is considered rare, the polyQ diseases constitute the largest group of monogenic neurodegenerative disorders. The disease appearances are usually observed when the number of glutamines is beyond ~35-45 (Table ). However, for SCA6, the pathological threshold is ~20 repeats, and for DRPLA and SCA3 it is ~50-55 repeats (Table ). Table . Polyglutamine (polyQ) repeat expansion diseases