Degenerative Myelopathy Breed Risk

Degenerative myelopathy (DM) is linked to a mutation in the SOD1 gene. Dogs with two copies of the mutation (A/A) are far more likely to develop DM than carriers with one copy (A/N) or dogs with none (N/N) — but even among A/A dogs, most don't develop it before other causes of death. A 2014 study genotyped over 33,000 dogs across 222 breeds; here's the frequency for the 65 breeds it tested in large enough numbers to report.

What A/A actually means for your dog

Genotype isn't diagnosis. In the same paper's own small owner-survey follow-up (137 dogs across 17 breeds, genotyped young and re-checked at 10+ years old), 60% of A/A dogs had developed DM-consistent signs by the time they were re-surveyed — meaning 40% hadn't. Only 4% of A/N carriers had, about the same rate as dogs with no mutant copies at all (6%). So a carrier (A/N) result carries little added risk; an A/A result raises real risk but isn't a certainty. A genetic test through your vet (not the frequency table below) is the only way to know your own dog's genotype — DM is also diagnosed by ruling out other causes of hind-limb weakness, not by genotype alone.

What this can't tell you

This table covers 65 of the 222 breeds the study genotyped — the ones tested in large enough numbers (50+ dogs) for the paper to report a reliable frequency. A breed not listed here means we don't have that breed's numbers, not that the mutation is absent in it.