Sphingomyelinosis (Variant 2)

Sphingomyelinosis causes progressive incoordination and tremors, enlargement of the spleen and liver, and changes in the lungs.

Key Signs

Progressive tremors, Severe ataxia, Epileptiform seizures

Age of Onset

0 to 2 yrs

Juvenile onset

Inheritance

Autosomal Recessive

For autosomal recessive disorders, cats with two copies of the variant are at risk of developing the condition. Cats with one copy of the variant are considered carriers and are usually not at risk of developing the disorder. However, carriers of some complex variants grouped in this category may be associated with a low risk of developing the disorder. Individuals with one or two copies may pass the disorder-associated variant to their kittens if bred.

Likelihood of the Condition

High likelihood

At risk cats are highly likely to show signs of this disease in their lifetime.

What to Do

Here’s how to care for a cat with Sphingomyelinosis

Partner with your veterinarian to make a plan regarding your cat’s well-being, including any insights provided through genetic testing. If your pet is at risk or is showing signs of this disorder, then the first step is to speak with your veterinarian.

For Veterinarians

Here’s what a vet needs to know about Sphingomyelinosis

Sphingomyelinosis (Variant 2) disorder is a lysosomal storage disease that is due to the lack of sphingomyelinase enzyme production. This results in an accumulation of sphingomyelin and cholesterol within lysosomes of neurons and other soft tissue cell types, such as liver, spleen, kidneys and lungs. Clinical signs in cats are usually evident at three months of age. Affected kittens exhibit intention tremors of the head and body and have a reduced menace response. Additionally, epileptiform seizures may appear. Other features of the disease may include enlargement of the spleen and liver along with changes to the lungs. The progression of the disease is rapid, leading to severe ataxia and motor dysfunction with an inability to move and stand by eight to ten months of age. The prognosis of the disease is grave due to its progressive nature.

As there is no cure for this disease, therapy is limited to supportive care. Quality of life of affected individuals should be monitored closely. The lifespan of an affected cat is dependent on the severity of the individual's condition, with most euthanized for welfare reasons before one year of age.

For Breeders

Planning to breed a cat with this genetic variant?

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 Sphingomyelinosis mutation can be safely bred with a clear cat with no copies of the Sphingomyelinosis mutation. About half of the kittens will have one copy (carriers) and half will have no copies of the Sphingomyelinosis 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 Sphingomyelinosis mutation could develop due to a different genetic or clinical cause.

Technical Details

Gene	NPC2
Variant	G>A
Chromosome	B3
Coordinate	121,872,988

All coordinates reference FelCat9.0

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References & Credit

Credit to our scientific colleagues:

Zampieri, S., Bianchi, E., Cantile, C., Saleri, R., Bembi, B., & Dardis, A. (2014). Characterization of a spontaneous novel mutation in the NPC2 gene in a cat affected by niemann pick type c disease. PLoS ONE, 9(11). View the article