What is Degenerative Myelopathy (DM)?
July 14, 2020
How do you best apply an Embark health variant test result to your breeding program or to an individual dog’s health care? When our veterinary geneticists and professional services team at Embark field questions like these, our answers are always based on the scientific research behind the health variant in question, as well as the breed of dog tested. We asked our experts to share answers to common questions about the tested variant for Degenerative Myelopathy (SOD1A).
What is Degenerative Myelopathy (DM)?
A disease of mature dogs, DM is a progressive degenerative disorder of the spinal cord that can cause muscle wasting and gait abnormalities. Affected dogs do not usually show signs until they are at least 8 years old, where the first signs of neural degeneration appear in the nerves that innervate the hind limbs. An affected dog may scuff the tops of their hind paws or walk with a hesitant, exaggerated gait.
In advanced cases, lower motor neurons are also affected leading to weakness and muscle wasting. This variant is reported to have incomplete penetrance, meaning not all dogs with two copies of the variant will go on to develop clinical signs and other genetic and environmental factors will contribute to whether a dog develops DM. Furthermore, this variant is only known to increase the risk of DM in certain breeds. Other breeds where this variant occurs but is not associated with DM risk likely have genetic factors protecting them from this disease.
My dog has two copies of this variant and is listed as having increased risk for DM; now what?
First, it is important to remember that the SOD1A variant is incompletely penetrant, so even in breeds where DM is a problem, many dogs testing at-risk from the variant will live long lives and never develop the disease.
If your dog is considered at-risk, this should open the door to a discussion with your veterinarian. As DM is a late-onset condition and genetic risk does not mean that clinical signs are guaranteed, drastic measures should not be an immediate concern. However, there are supplements and lifestyle modifications that may be of benefit to your dog.
Some non-medical things that can help with mobility and secondary injury to the feet include a harness (Help ‘Em Up Harness is a popular option) as well as using booties to minimize damage to nails from scuffing. Be sure to take the booties off when not in use as they can trap moisture and lead to infection.
My dog has two copies of this variant but is not listed as having increased risk for DM; now what?
For some breeds, research indicates that the SOD1A variant is not likely to increase the risk that a dog will develop DM. The SOD1A variant is found in many breeds of dogs, but researchers have only observed histopathological (microscopic) changes with this variant in a small number of breeds.
When determining whether or not a variant is expected to have a clinical impact for a breed, we have taken into account research either published, internal, or otherwise presented by a subject matter authority as our primary criteria. For breeds where clinical risk from this variant is not likely, this genetic result should not be the primary factor in breeding decisions.
What does it mean if my dog is a carrier?
As DM has an autosomal recessive mode of inheritance, dogs with one copy of the variant would be termed “carriers” and not be expected to be at clinical risk. However, in breeds where the SOD1A mutation is associated with DM risk, carriers should not be bred to other carriers (or at-risk dogs) as this will lead to the production of at-risk puppies. You can visit our website and search for your breed. If the “Embark Recommended” icon appears next to Degenerative Myelopathy (SOD1A), then there is a known risk based on the current literature, and this result may need to be considered in breeding decisions.
For all other breeds, while it is still important to track the incidence of the variant and clinical disease within lines to inform on future research, it is not recommended that this variant be used as the primary factor in breeding decisions, at this time. (Also, please note that the OFA will register DM results for any breed, so an OFA icon only indicates that it can be registered with the OFA and does not confer impact to the breed.)
How can I help with research?
We are interested to learn about the clinical impact of the SOD1A mutation in more breeds. If you know of dogs that have been definitively diagnosed with DM (via histopathology), and have tested as having one or two copies of the SOD1A mutation, we would appreciate that information for consideration during our health review process.
Additionally, we’d like to hear from you about any health conditions a dog is diagnosed with. Please fill out our Annual Health Survey If you have not yet done so; your responses will help us help all dogs.
Where can I learn more ?
Understanding the genetic research behind your Embark test results can help you better assess them, so you can make confident breeding decisions.
- Read the electronic breed reports we’ve created, showing health and coat color allele frequency for Embark tested dogs opted into research. You can contact us to see if your breed has a report available.
- Learn more about how to apply genetic health results in the context of breed allele frequency, by watching this educational video from our CSO, Dr. Adam Boyko.