GM2 Gangliosidosis Type II (Discovered in Japanese domestic cats)

GM2 Gangliosidoses are a group of neurodegenerative disorders caused by dysfunction in lysosomal storage. There are different types and causes of the disease. This form of the disease is caused by reduced activity of the beta-hexosaminidase enzyme. Deficiency of this enzyme leads to accumulation of GM2 ganglioside within the lysosomes of neurons. This accumulation then leads to cellular dysfunction, degeneration, and eventual neuronal death. Clinical signs include progressive neurologic symptoms and visual defects. The onset of clinical signs occurs at approximately six to eight weeks of age. The first clinical signs are mild intention tremors. The disease rapidly progresses to severe ambulatory difficulties due to whole body tremors, severe ataxia, loss of balance, quadriparesis, difficulty eating, and blindness. Affected cats are usually smaller than normal in body size and weight. Affected kittens are usually euthanized on welfare grounds by six months of age. Five different mutations in the HEXB gene have been found as causative mutations for the disease, all in different breeds.

Upon initial observation of clinical signs, affected cats should be closely monitored to assess welfare and devise a supportive care treatment plan. As clinical signs are progressive, affected cats are usually euthanized on welfare grounds by six months of age.

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

This disease is autosomal recessive meaning that two copies of the mutation are needed for disease signs to be shown. A carrier cat with one copy of the GM2 Gangliosidosis mutation can be safely bred with a clear cat with no copies of the GM2 Gangliosidosis mutation. About half of the kittens will have one copy (carriers) and half will have no copies of the GM2 Gangliosidosis mutation. Kittens 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 kittens. Please note: It is possible that disease signs similar to the ones caused by the GM2 Gangliosidosis mutation could develop due to a different genetic or clinical cause.