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.
Mucopolysaccharidosis Type VII (MPS VII) is a lysosomal storage disease caused by deficient activity of the beta-glucuronidase enzyme. Deficiency of the beta-glucuronidase enzyme leads to accumulation of glycosaminoglycans (GAGs) in various types of cells which eventually progresses to cellular damage. Clinical signs of the disease are typically evident at eight weeks of age. Affected kittens exhibit stunted growth and several skeletal deformities including dysmorphic facial features. Affected cats develop progressive paralysis/paresis of the limbs and clouding of the corneas. The prognosis of the disease is grave due to its progressive nature. In humans, MPS VII is known as Sly syndrome.
There is high interest in research for safe and effective treatments of MPS disorders in cats, with options such as enzyme replacement therapy and gene therapy showing promise. At present time, however, the most widely available therapy is limited to supportive care, including pain alleviation and physiotherapy. The lifespan of an affected cat is dependent on the severity of the individual's condition but, due to the progressive nature of this disorder, affected cats are often euthanized for welfare reasons at a young 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 MPS7 mutation can be safely bred with a clear cat with no copies of the MPS7 mutation. About half of the kittens will have one copy (carriers) and half will have no copies of the MPS7 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 MPS7 mutation could develop due to a different genetic or clinical cause.
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Wang, P., Sorenson, J., Strickland, S., Mingus, C., Haskins, M. E., & Giger, U. (2015). Mucopolysaccharidosis VII in a cat caused by 2 adjacent missense mutations in the GUSB gene. Journal of Veterinary Internal Medicine, 29(4), 1022–1028. View the article