Fetal Onset Neuroaxonal Dystrophy

Fetal Onset Neuroaxonal Dystrophy (FNAD) is a disorder that disturbs the development of motor (movement) nerves in the central nervous system. Signs include abnormal curvature of the spine and contracted joints. Affected puppies to have no voluntary movement of limbs. Respiratory deficiencies (difficulties breathing) cause affected puppies to die at birth.

Key Signs

Respiratory failure, Arthrogryposis. Scoliosis, Hypoplasia of lungs / brain / spine, Death upon birth

Age of Onset

At birth

Present at birth

Inheritance

Autosomal Recessive

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.

Likelihood of the Condition

High likelihood

At risk dogs are highly likely to show signs of this disease in their lifetime.

What to Do

Here’s how to care for a dog with FNAD

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.

For Veterinarians

Here’s what a vet needs to know about FNAD

Fetal onset neuroaxonal dystrophy (FNAD) is a disorder that disturbs the development of motor neurons in the central nervous system. Scoliosis (abnormal lateral curvature of the spine) and multiple contracted joints (arthrogryposis) are often observed. Arthrogryposis causes affected puppies to have no voluntary movement of limbs. Respiratory deficiencies cause affected puppies to die at birth.

Post-mortem examination to confirm disease. Post-mortem examinations usually reveal abnormally swollen axons throughout the brain stem, spinal cord, and peripheral nerves.

For Breeders

Planning to breed a dog with this genetic variant?

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 FNAD mutation can be safely bred with a clear dog with no copies of the FNAD mutation. About half of the puppies will have one copy (carriers) and half will have no copies of the FNAD mutation. Puppies in a litter which is expected to contain carriers should be tested prior to breeding. Carrier to carrier matings should not be undertaken as resulting litters may containing affected puppies. Please note: It is possible that disease signs similar to the ones caused by the FNAD mutation could develop due to a different genetic or clinical cause.

Technical Details

Gene	MFN2
Variant	G>C
Chromosome	2
Coordinate Start	84,289,961
Coordinate End	84,289,959

All coordinates reference CanFam3.1

References & Credit

Credit to our scientific colleagues:

Fyfe, J. C., Al-Tamimi, R. A., Liu, J., Schäffer, A. A., Agarwala, R., & Henthorn, P. S. (2011). A novel mitofusin 2 mutation causes canine fetal-onset neuroaxonal dystrophy. Neurogenetics. View the article