Mucopolysaccharidosis VII (Shepherd Type)

Common Symptoms

Mucopolysaccharidosis (MPS) VII (shepherd type) is an inherited Lysosomal Storage Disorder affecting dogs. Affected dogs have insufficient activity of the Enzyme beta-glucuronidase, which is responsible for breaking down glycosaminoglycans (GAGs). GAGs are an important component of Connective Tissue. In affected dogs, there is an accumulation of breakdown products in cells causing abnormal growth and function of various organ systems. Clinical signs of MPS VII are most commonly associated with accumulations in the bones and joints. Therefore, affected dogs typically present between 4 to 8 weeks of age with symptoms of bone and joint disease. Affected puppies have disproportionally large heads with short muzzles, broad faces, low-set ears and domed skulls. Other skeletal deformities include broad chests, joint laxity and deformed, crooked legs resulting in an inability to walk by 5 months of age. Affected puppies also have cloudy eyes and are smaller than their normal littermates. Dogs may also present with heart problems. While affected dogs can survive with assistance for several years, they are often euthanized due to a poor quality of life.

Breed-Specific Information for the Belgian Malinois

The Mutation of the GUSB gene associated with mucopolysaccharidosis VII (shepherd type) has been identified in the Belgian malinois in the Paw Print Genetics laboratory. The frequency of the causal mutation has not been reported in the medical literature for the Belgian malinois.  It is unknown at this time if dogs carrying two copies of this mutation for this breed develop the clinical signs of mucopolysaccharidosis VII (shepherd type).

Testing Tips

Genetic testing of the GUSB gene in the Belgian malinois will reliably determine whether a dog is a genetic Carrier of mucopolysaccharidosis VII (shepherd type). Mucopolysaccharidosis VII (shepherd 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 GUSB gene mutation. Reliable genetic testing is important for determining breeding practices. 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. Belgian malinois 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

• Haskins ME, Aguirre GD, Jezyk PF, Schuchman EH, Desnick RJ, Patterson DF. Mucopoysaccharidosis type VII (Sly Syndrome). Beta-glucuronidase-deficient mucopolysaccharidosis in the dog. Am J Pathol. 1991 Jun;138(6):1553-5. [PubMed: 1905109]
• Ray J, Bouvet A, DeSanto C, Fyfe JC, Xu D, Wolfe JH, Aguirre GD, Patterson DF, Haskins ME, Henthorn PS. Cloning of the canine beta-glucuronidase cDNA, mutation identification in canine MPS VII, and retroviral vector-mediated correction of MPS VII cells. Genomics. 1998 Mar 1; 48(2):248-53. [PubMed: 9521879]
• Ray J, Haskins ME, Ray K. Am J Vet Res. Molecular diagnostic tests for ascertainment of genotype at the mucopolysaccharidosis type VII locus in dogs. 1998 Sep; 59(9):1092-5. [PubMed: 9736382]
• Silverstein Dombrowski DC, Carmichael KP, Wang P, O'Malley TM, Haskins ME, Giger U. Mucopolysaccharidosis type VII in a German Shepherd Dog. J Am Vet Med Assoc. 2004 Feb 15;224(4):553-7, 532-3. [PubMed: 14989549]