Mucopolysaccharidosis type IIIA is characterized by central nervous system degeneration, with subsequent progressive ataxia (uncoordinated movement) and hypermetria (exaggerated high-stepping gait) due to inappropriate accumulation of glycosaminoglycans. The first signs of ataxia can be seen in pelvic limbs, progressing to all four limbs. The clinical signs include dysmetric gait, loss of learned behavior, difficulty jumping, and loss of balance. First clinical signs are usually observed at one to two years of age. Affected dogs are usually euthanized within a few months of onset of clinical signs.

This disorder is progressive with no cure. Affected dogs should be closely monitored to assess welfare and devise a supportive care treatment plan. Due to the progressive nature of the disease, affected dogs are often euthanized for welfare reasons within a few months of diagnosis.

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.