Signs include behavioral changes and signs of physical dysfunction that, on average, start 1-2 years of age, with some signs starting as early as 4-6 months. Affected dogs exhibit abnormal behavior patterns, may be aggressive or depressed, and appear "forgetful". Other signs include appearing unsteady on their feet, blindness and deafness, and may suffer from gastrointestinal problems. The disease can appear to progress rapidly, and death or euthanasia usually occurs within a few weeks from the onset of clinical signs. Nearly all dogs with this disease die or are put to sleep by 4 years.