Neuronal ceroid lipofuscinosis (NCL) is a rare group of lethal neurodegenerative lysosomal storage diseases, in which a homozygous single base-pair deletion (c.846delT) in the canine CLN7/MFSD8 gene has been identified as a causative mutation in Chihuahuas. The gene discussed is MFSD8; the disease is lysosomal storage disease.