CLN8 and neuronal ceroid lipofuscinosis 8 northern epilepsy variant: Certain homozygous or compound heterozygous CLN8 mutations cause two distinct variants of neuronal ceroid lipofuscinosis-8 (OMIM#600143): Northern epilepsy variant (OMIM#610003), also known as progressive epilepsy with mental retardation (EPMR; [4]), and a more severe form of variant late-infantile neuronal ceroid lipofuscinosis [5].