Neuronal ceroid lipofuscinosis 12 is an inherited lysosomal storage disease affecting dogs. Affected dogs have abnormalities in cellular metabolism. As a result, there is an abnormal accumulation of waste compounds primarily in the cells of the nervous system. Affected dogs present with progressive neurological disease around 6 years of age which may include abnormal gait, anxiety, decreased or absent reflexes, lack of response to learned commands, sensitivity to sounds, sleep problems, inappropriate vocalization, difficulty jumping or climbing stairs, aggression, tremors, seizures, weakness, loss of coordination, and vision loss. Affected dogs typically die or are humanely euthanized by 9 years of age.