Neuronal ceroid lipofuscinosis 7 (NCL7) is a lysosomal storage disease affecting Chihuahuas. Affected dogs lack a specific Enzyme necessary for normal metabolism. As a result, there is an abnormal accumulation of waste compounds in cells which affects the normal function of the brain and nervous system. Affected dogs typically present around 1 to 2 years of age with a variety of progressive neurological symptoms including behavioral and personality changes, disorientation, sensitivity to loud noises, abnormal gait, wide-based stance, vision loss, decreased reflexes, and seizures. Most affected dogs will die or be humanely euthanized by 2 to 3 years of age.