Neuroaxonal Dystrophy (Giant Schnauzer Type)

Common Symptoms

Neuroaxonal dystrophy is an inherited neuromuscular disorder affecting giant schnauzers. This disorder affects the function of the motor nerve cells and disrupts normal muscle movement In Utero. Affected puppies die of respiratory failure at birth due to underdeveloped lungs. Their joints are contracted and immobile and their spines are curved. This condition is lethal because affected puppies cannot breathe on their own.

Breed-Specific Information for the Giant Schnauzer

Giant schnauzers are included as a breed susceptible to neuroaxonal dystrophy because the Mutation of the MFN2 gene associated with this disease was identified in the offspring of a purebred beagle and purebred giant schnauzer. The frequency of the causal mutation in the general giant schnauzer population is unknown.

Testing Tips

Genetic testing of the MFN2 gene in giant schnauzers will reliably determine whether a dog is a genetic Carrier of neuroaxonal dystrophy. Neuroaxonal dystrophy 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 MFN2 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. Giant schnauzers 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

• Fyfe JC, Al-Tamimi RA, Castellani RJ, Rosenstein D, Goldowitz D, Henthorn PS. Inherited neuroaxonal dystrophy in dogs causing lethal, fetal-onset motor system dysfunction and cerebellar hypoplasia. J Comp Neurol. 2010 Sep 15;518(18):3771-84. [PubMed: 20653033]
• Fyfe JC, Al-Tamimi RA, Liu J, Schäffer AA, Agarwala R, Henthorn PS. Neurogenetics. A novel mitofusin 2 mutation causes canine fetal-onset neuroaxonal dystrophy. 2011 Aug; 12(3):223-32. [PubMed: 21643798]