The CLN3 subtype (resulting from mutations in the CLN3 gene and referred to here as CLN3 disease) is the most common form of Batten disease in the United States and Europe (Wisniewski et al., 1998), and has a juvenile onset of symptoms between 4 and 7 years of life (Hofmann et al., 1999). The gene discussed is CLN3; the disease is glycogen storage disease VI.