Each form of NCL is caused by mutations in a different gene (CLN1, OMIM #256730; CLN2, OMIM #204500; CLN3, OMIM #204200; CLN4, OMIM #204300; CLN5, OMIM #256731; CLN6, OMIM #601780; CLN7, OMIM #610951; CLN8, OMIM #600143; CLN9, OMIM #609055; CLN10, OMIM #610127; CLN11, OMIM #614706; CLN12, OMIM #256730 and CLN13, OMIM #615362), which determines the progression and severity of the disease, although they all lead to the death of the patient after a period of prolonged disability (Refs 38–40). This evidence concerns the gene CLN3 and neuronal ceroid lipofuscinosis.