Mucopolysaccharidosis type IIIA is characterized by progressive ataxia (uncoordinated movements), and first clinical signs are usually observed in the third year of life. The signs of ataxia are initially seen in pelvic limbs progressing later to all four limbs. The clinical signs include dysmetric gait and loss of balance. An affected dog may also sway while standing.

This disorder is progressive with no cure. Wellbeing of affected dogs should be monitored. Owners should be advised that as clinical signs progress, affected dogs may have difficulties on smooth surfaces and with climbing stairs. Euthanasia is often elected on welfare grounds when clinical signs become severe.

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 IIIA mutation can be safely bred with a clear dog with no copies of the MPS IIIA mutation. About half of the puppies will have one copy (carriers) and half will have no copies of the MPS IIIA 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 IIIA mutation could develop due to a different genetic or clinical cause.