Below is an instruction from Human. Write a response.
    ### Instruction:
    How many people are affected by dentatorubral-pallidoluysian atrophy ?
    ### Response:
    DRPLA is most common in the Japanese population, where it has an estimated incidence of 2 to 7 per million people. This condition has also been seen in families from North America and Europe.  Although DRPLA is rare in the United States, it has been studied in a large African American family from the Haw River area of North Carolina.
    