Neuro-axonal dystrophy (NAD) in Papillon dogs is a rare inherited neurological disorder that causes progressive degeneration of the central nervous system. Signs appear very early, usually between 2 and 4 months of age, and include gait abnormalities, head and limb tremors, weakness of the hind limbs, and in some cases, involvement of the forelimbs or visual deficits. The progression is rapid and severe: affected dogs may have difficulty eating and are often euthanized shortly after the onset of symptoms due to a reserved vital prognosis.
