What this means is that a presumptive diagnosis of DM can only be made by ruling out other causes of spinal cord disease (e.g., herniated intervertebral disk, tumor, infection, trauma). Making the diagnosis of degenerative myelopathyĭM is a “rule out diagnosis”. It is also reasonable to have the puppy tested prior to purchase, although, if the parents have been tested and have “normal” results, this is unnecessary. If contemplating purchasing a pup of an at-risk breed, it is important to request DM test results for the dam and sire of the litter of interest. Responsible breeders utilize DNA testing for DM to help assess whether or not a particular dog is suitable for breeding purposes. This is because not all dogs with two mutated copies of the gene go on to develop DM. It is important to remember that DNA testing does not diagnose DM.
This DNA test identifies dogs that are normal (have two normal copies of the gene), those who are carriers (have one normal copy of the gene and one mutated copy), and those who are at risk for development of DM (have two mutated copies of the gene). All that is required is a blood sample or cheek swab. This test is available through the Orthopedic Foundation for Animals (OFA). Testing is available to determine an individual dog’s SOD1 mutation status. Genetic testing for d egenerative myelopathy
What remains unknown is why some dogs who have this “double mutation” never develop symptoms of DM. In order for a dog to be affected, the mutation must be inherited from both dam and sire. The researchers discovered that DM has a recessive mode of inheritance. Their study involved Boxers, Pembroke Welsh Corgis, German Shepherds, Chesapeake Bay Retrievers, and Rhodesian Ridgebacks. In 2008 a group of researchers reported through Texas A&M University that a genetic mutation on the SOD1 gene is a major risk factor for the development of DM. Given enough time, the disease progresses toward the head end of the body, causing loss of front leg function as well.ĭM is an inherited disease. This explains why the hind limbs are more severely affected. These degenerative changes begin in the thoracolumbar region of the spinal cord, the portion that lines up with the end of the rib cage. Difficulty supporting weight with hind legsĪlthough this degenerative process is not painful, affected dogs can develop discomfort because of overuse of other body parts attempting to compensate for the hind end weakness.ĭM causes degenerative changes within spinal cord axons, structures that transmit information back and forth between the brain and the rest of the body.Knuckling of hind feet (weight bearing on the tops of the feet rather than their undersides).Hind end weakness (difficulty climbing stairs, jumping up into the car, going for walks).Dragging the hind feet causing wearing down of the toenails.Loss of coordination (ataxia) in the hind legs.
The symptoms typically progress as follows: From beginning to end, DM affected dogs typically remain alert and animated. The breeds most commonly affected include the German Shepherd, Pembroke Welsh Corgi, Cardigan Welsh Corgi, Boxer, Borzoi, Rhodesian Ridgeback, American Eskimo Dog, Bernese Mountain Dog, Golden Retriever, Great Pyrenees, Kerry Blue Terrier, Poodle, Pug, Shetland Sheepdog, Soft Coated Wheaten Terrier, Wire Fox Terrier, and Chesapeake Bay Retriever.ĭM symptoms progress slowly over the course of months to even years. We now know that DM occurs in many purebred and mixed breed dogs. Back in the day (when I was just a pup) we referred to this disease as German Shepherd Myelopathy because we thought it was unique to this breed. The inevitable result for dogs with DM is paraplegia-hind end paralysis.ĭM affects primarily older dogs, with symptoms typically beginning at eight years of age or older. Degenerative myelopathy (DM) is a slowly progressive spinal cord disorder that resembles Amyotrophic Lateral Sclerosis (ALS or Lou Gehrig’s Disease) in people.
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