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.
At risk cats are highly likely to show signs of this disease in their lifetime.
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.
Sphingomyelinosis (Variant 1) 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 may be evident as young as nine to twelve weeks of age. Affected kittens exhibit intention tremors of the head and body and may demonstrate a progressive hypermetric gait. Other features of the disease 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 eventual inability to move and stand. Some affected individuals display a characteristic chewing motion and may have seizures. The prognosis for 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.
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.
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Somers, K. L., Royals, M. A., Carstea, E. D., Rafi, M. A., Wenger, D. A., & Thrall, M. A. (2003). Mutation analysis of feline Niemann-Pick C1 disease. Molecular Genetics and Metabolism, 79(2), 99–103. View the article