Degenerative myelopathy (DM)

How it is done

DNA test

What it looks for

The SOD1 c.118G>A allele associated with degenerative myelopathy, an inherited neurological disorder the laboratory compares to Lou Gehrig's disease in people.

Why it matters

Affected dogs usually start showing signs in adulthood, at least 8 years of age: gradual muscle wasting and loss of coordination that begins in the hind limbs because the nerves are degenerating. It keeps progressing until the dog cannot walk. Late on, dogs may become incontinent and the front limbs may be affected. Affected dogs may lose the ability to walk entirely six months to two years after the first signs. Small breed dogs tend to progress more slowly.

How it is done

A DNA test on cells brushed from the dog's cheeks and gums with a cytology brush; the laboratory supplies the brushes. The dog must not have eaten or drunk for at least an hour beforehand, and the laboratory recommends waiting until puppies are at least three weeks old.

How it is inherited

Autosomal recessive with incomplete penetrance. A dog with N/N will not have degenerative myelopathy and cannot pass the allele on. A dog with N/DM will not develop the disease from this allele but is a carrier and passes it to 50% of its offspring; two carriers mated together are predicted to produce 25% of puppies at risk. A dog with DM/DM may have degenerative myelopathy and passes the allele to all of its offspring. Crucially, not all DM/DM dogs develop the disease: the variable presentation between breeds and the incomplete penetrance show that DM is not simply inherited but has a complex mode of inheritance, with other genetic and environmental factors likely involved.

For the breed

General to all breeds

What the results mean

• N/N — Two normal copies. The dog will not have degenerative myelopathy and cannot transmit this allele to its offspring.
• N/DM — Carrier. The dog will not have degenerative myelopathy as a result of this allele but transmits it to 50% of its offspring; carrier x carrier is predicted to produce 25% of puppies at risk.
• DM/DM — Two copies of the allele. The dog may have degenerative myelopathy, a disabling condition, and transmits the allele to all of its offspring - but not every DM/DM dog develops the disease.

Where the result is recorded

• Orthopedic Foundation for Animals (OFA)

Source: Degenerative Myelopathy (DM) - test page, Veterinary Genetics Laboratory, UC Davis School of Veterinary Medicine, Quick Summary; Phenotype; Mode of Inheritance; Alleles; Breeds appropriate for testing; Explanation of Results; Sample Collection; Additional Details (No version label published on the page; content as retrieved 2026-08-11) — https://vgl.ucdavis.edu/test/degenerative-myelopathy · Explanations checked: 2026-08-11

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Explanations checked: 11 August 2026