The first clinical signs of inherited narcolepsy are usually observed by 6 months of age. A typical sign of narcolepsy is excessive daytime drowsiness or decreased daytime activity compared to dogs of the same breed and age. The clinical signs also include cataplexic episodes characterized by sudden loss of muscle tone. Cataplexic episodes start with the dog's hind limbs bending and neck hanging down followed by a collapse which might result in the dog laying down for several seconds or minutes. An affected dog may try to resist the attack which can be seen as a wobbly gait and hind limb weakness. The dog usually stays conscious and alert especially in the beginning of the episode. However, if the attack lasts longer than a couple of minutes, the dog may fall asleep. In longer episodes, fast eye movement characteristic for REM sleep can be observed. Muscle twitches and slow repetitive muscle movements are also possible. Unlike in epileptic seizures, muscles are relaxed during cataplexic episodes and no drooling, urinating, or defecation is observed. Feeding and playing with the dog can provoke cataplexic episodes.

Drug therapy to reduce the cataplexy may considered as needed. Otherwise, dogs with narcolepsy appear to have a normal lifespan.

There are many responsibilities to consider when breeding dogs. Regardless of test results it is important that your dog is in good general health and that you are in a position to care for the puppies if new responsible owners are not found. For first time or novice breeders, advice can be found at most kennel club websites.

This disease is autosomal recessive meaning that two copies of the mutation are needed for disease signs to occur. A carrier dog with one copy of the Narcolepsy mutation can be safely bred with a clear dog with no copies of the Narcolepsy mutation. About half of the puppies will have one copy (carriers) and half will have no copies of the Narcolepsy mutation. Puppies in a litter which is expected to contain carriers should be tested prior to breeding. Carrier to carrier matings are not advised as the resulting litter may contain affected puppies. Please note: It is possible that disease signs similar to the ones caused by the Narcolepsy mutation could develop due to a different genetic or clinical cause.