Demyelinating polyneuropathy in Miniature Schnauzers typically present with regurgitation due to megaesophagus and aphonic bark. Megaesophagus is when the esophagus gets larger and loses its ability to move food into the stomach, and aphonic bark is the dog equivalent of losing your voice. Age of onset is typically less than two years.
There is no cure for Demyelinating polyneuropathy and treatment is aimed at improving clinical signs. The disease can progress and lead to pelvic limb weakness and muscular atrophy in a small number of cases. However, in most affected dogs the clinical signs remain unchanged for up to seven years, and dogs have a fair prognosis if complications such as aspiration pneumonia and anorexia can be avoided.
The single nucleotide substitution in the gene called MTMR13 that causes Demyelinating Polyneuropathy in Miniature Schnauzer is autosomal recessive. This means that dogs that carry two copies of the mutation (homozygotes) will almost certainly develop Demyelinating Polyneuropathy during their lives. Dogs that carry a single copy of the mutation (also known as carriers or heterozygotes) will not develop Demyelinating Polyneuropathy as a result of the MTMR13 mutation, but they will pass the mutation onto about half of any offspring they have. Breeding dogs that will not develop Demyelinating Polyneuropathy should be the breeder’s priority, with a reduction in mutation frequency within the whole breed being the secondary, longer-term target.
Carriers can be bred from safely, provided they are mated to a dog that has also been tested and is clear of the MTMR13 mutation (i.e. carry no copies of the mutation). If a carrier is mated to a clear dog approximately half of the resulting puppies will also be carriers, so should be tested themselves prior to breeding. Breeding carriers to tested, clear dogs is safe, in terms of avoiding dogs affected with Demyelinating Polyneuropathy, and will help to maintain the genetic diversity of a breed. It is therefore encouraged, particularly in the first few generations following the availability of a new genetic test, so that other desirable characteristics and traits can be preserved before the frequency of the disease mutation within the breed is gradually reduced.