Below is an instruction from Human. Write a response.
    ### Instruction:
    How many people are affected by juvenile Batten disease ?
    ### Response:
    Juvenile Batten disease is the most common type of NCL, but its exact prevalence is unknown. Collectively, all forms of NCL affect an estimated 1 in 100,000 individuals worldwide. NCLs are more common in Finland, where approximately 1 in 12,500 individuals are affected.
    