Neuronal ceroid lipofuscinosis 4A (NCL4A) is an adult-onset, lysosomal storage disease affecting dogs. NCL4A is caused by deficiency in the activity of the Enzyme arylsulfatase G (ARSG), which is necessary to break down certain proteins in the cells. As a result there is an accumulation of these compounds in cells, which affects the normal function of the brain and nervous system. Affected dogs present between 3 to 5 years of age with slowly progressive neurologic disease. Symptoms include a lack of muscle coordination, tremors, abnormal eye movement, abnormal gait and difficulty in balancing and jumping. Dogs are often euthanized 2 to 4 years after initial disease symptoms when they can no longer walk. Rarely affected dogs can live a normal lifespan with mild symptoms.