For autosomal recessive disorders, dogs with two copies of the variant are at risk of developing the condition. Dogs 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 puppies if bred.
At risk dogs are highly likely to show signs of this disease in their lifetime.
Partner with your veterinarian to make a plan regarding your dog’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.
The first clinical signs of mucopolysaccharidosis VII can be seen in dogs 2 to 5 months of age and typically involves hind limb weakness that progresses to ataxia of all four limbs. The affected dogs also exhibit growth retardation, facial and other skeletal dysmorphisms, and corneal clouding. These dogs may show severe epiphyseal dysplasia when radiographed and exhibit extreme laxity of joints that can result in subluxation with minimal effort. Neutrophils and lymphocytes in the blood or CSF may have cytoplasmic granules. Several other organs may be involved showing hepatomegaly, tracheal dysplasia, and cardiac abnormalities. Affected puppies are usually euthanized because of the severity of the condition.
Treatment is supportive care, however, affected puppies are usually euthanized on welfare grounds because of the severity of the condition. Experimental gene therapy may prove curative in the future.
There are many responsibilities to consider when breeding dogs. Regardless of test results it is important that your dog is in good general health and that you are in a position to care for the puppies if new responsible owners are not found. For first time or novice breeders, advice can be found at most kennel club websites.
This disease is autosomal recessive meaning that two copies of the mutation are needed for disease signs to occur. A carrier dog with one copy of the MPS VII mutation can be safely bred with a clear dog with no copies of the MPS VII mutation. About half of the puppies will have one copy (carriers) and half will have no copies of the MPS VII mutation. Puppies 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 puppies. Please note: It is possible that disease signs similar to the ones caused by the MPS VII mutation could develop due to a different genetic or clinical cause.
All coordinates reference CanFam3.1
Ray, J., Bouvet, A., DeSanto, C., Fyfe, J. C., Xu, D., Wolfe, J. H., … Henthorn, P. S. (1998). Cloning of the canine β-glucuronidase cDNA, mutation identification in canine MPS VII, and retroviral vector-mediated correction of MPS VII cells. Genomics, 48(2), 248–253. View the article