Mucopolysaccharidosis IIIA (Dachshund Type)

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Common Symptoms

Mucopolysaccharidosis (MPS) IIIA (dachshund type) is an inherited Lysosomal Storage Disorder affecting dogs. Affected dogs have insufficient activity of the Enzyme heparan N-sulfatase which is responsible for breaking down heparan sulfate. Heparan sulfate is an important component of tissues throughout the body. In affected dogs, there is an accumulation of breakdown products in cells, especially those of the nervous system. Affected dogs typically present around 3 years of age with neurologic deterioration. Unlike other forms of mucopolysaccharidoses in dogs, MPS IIIA is primarily a progressive neurologic disease with more limited involvement of the joints and organs. Symptoms include Ataxia and loss of reflexes more severely affecting the hind limbs, head tremors, swaying, and abnormal eye movement. Although disease progression is slow, affected dogs are often euthanized within a few years of diagnosis.


Testing Tips

Genetic testing of the SGSH gene will reliably determine whether a dog is a genetic Carrier of mucopolysaccharidosis IIIA (dachshund type). Mucopolysaccharidosis IIIA (dachshund type) is inherited in an Autosomal Recessive manner in dogs meaning that they must receive two copies of the mutated gene (one from each parent) to develop the disease. In general, carrier dogs do not have features of the disease but when bred with another carrier of the same Mutation, there is a risk of having affected pups. Each pup that is born to this pairing has a 25% chance of inheriting the disease and a 50% chance of inheriting one copy and being a carrier of the SGSH gene mutation. Reliable genetic testing is important for determining breeding practices. Because symptoms do not appear until adulthood, genetic testing should be performed before breeding. In order to eliminate this mutation from breeding lines and to avoid the potential of producing affected pups, breeding of known carriers to each other is not recommended. Dogs that are not carriers of the mutation have no increased risk of having affected pups.


There may be other causes of this condition in dogs and a normal result does not exclude a different mutation in this gene or any other gene that may result in a similar genetic disease or trait.


References

  • Arnovich EL, Carmichael KP, Morizono H, Koutlas IG, Deanching M, Hoganson G, Fischer A, Whitley CB. Canine heparin sulfate sulfamidase and the molecular pathology underlying Sanfilippo syndrome type A in Dachshunds. Genomics. 2000 Aug 15; 68(1):80-4. [PubMed: 10950929]
  • Fischer A, Carmichael KP, Munnell JF, Jhabvala P, Thompson JN, Matalon R, Jezyk PF, Wang P, Giger U. Sulfamidase deficiency in a family of Dachshunds: A canine model of mucopolysaccharidosis IIIA (Sanfilippo A). Pediatr Res. 1998 July;44(1):74–82. [PubMed: 9667374]