Degenerative Myelopathy in German Shepherds: What Breeders and Puppy Buyers Should Really Know
When families begin researching German Shepherd breeders, one abbreviation often creates immediate concern:
DM.
You may see terms like:
• DM Clear• DM Carrier• DM At Risk
And for someone who has never studied canine genetics, the word “carrier” can sound frightening.
But what does it actually mean?
Does a DM carrier have Degenerative Myelopathy?
Will a carrier become sick?
Should a carrier ever be bred?
And does breeding a DM-clear dog to a DM carrier put the puppies in danger?
The answers are much more reassuring — and much more interesting — than many people realize.
What Is Degenerative Myelopathy?
Degenerative Myelopathy, commonly called DM, is a progressive neurologic disease that affects the spinal cord.
It usually occurs later in life.
Early signs can include:
• Weakness in the rear legs• Loss of coordination• Dragging or scuffing the rear feet• Difficulty getting up• Gradually increasing hind-end weakness
In dogs that truly develop DM, the disease can progress over time and eventually cause significant paralysis.
German Shepherd Dogs are one of the breeds in which DM has been recognized, so responsible breeders should absolutely take the disease seriously.
But there is something extremely important to understand:
A DNA test for DM does not diagnose a dog with Degenerative Myelopathy.
The commonly used DNA test looks for a particular mutation in the SOD1 gene that is associated with an increased risk of developing the disease.
That distinction matters.
What Does the DM DNA Test Actually Tell Us?
The common SOD1 test generally gives one of three results:
N/N — Clear
The dog has two normal copies of the tested gene.
This dog is considered clear for the tested SOD1 mutation and will not pass that particular mutation to its puppies.
N/DM — Carrier
The dog has:
• One normal copy• One copy of the DM-associated mutation
This dog is called a carrier.
And this is where there is often unnecessary confusion.
A carrier is not the same thing as a genetically at-risk dog.
UC Davis describes N/DM dogs as carriers that are not expected to develop DM as a result of this particular allele, although they can transmit the mutation to approximately half of their offspring.
The OFA and University of Missouri likewise distinguish carriers from dogs with two copies of the risk allele.
The OFA notes that carriers are far less likely to develop DM and may be used carefully in breeding programs.
DM/DM — At Risk
A dog that inherits the mutation from both parents has two copies.
This dog is considered genetically at risk for developing DM.
But even this result does not mean:
“This dog definitely will develop DM.”
DM has what geneticists call incomplete penetrance.
That means some dogs with two copies of the risk mutation never develop clinical disease during their lifetime.
That is one reason DM genetics are more complicated than simply labeling dogs “good” or “bad.”
Can a DM Carrier Be Bred Responsibly?
Yes.
This is probably one of the most misunderstood parts of DM testing.
A genetically valuable German Shepherd that is a DM carrier does not automatically need to be removed from a breeding program.
The important question is:
What is that carrier bred to?
If a DM carrier is bred to a DM-clear dog, the puppies are expected to be:
Approximately 50% clear
and
Approximately 50% carriers.
Most importantly:
None should inherit two copies of the tested DM mutation.
In other words:
Clear × Carrier does not produce DM/DM puppies.
The carrier puppies can inherit one copy, but they do not inherit two copies of the mutation.
That is why knowledgeable genetic management focuses on appropriate mating combinations, rather than simply eliminating every carrier from a breed.
A Simple DM Inheritance Example
Imagine the following breeding:
Father: DM ClearN/N
Mother: DM CarrierN/DM
The father can only pass:
N
The mother can pass either:
N
or
DM
The puppies can therefore be:
N/N — Clear
or
N/DM — Carrier
There is no genetic combination in this mating that produces:
DM/DM — At Risk
That is the key.
Why Not Simply Breed Only DM-Clear Dogs?
At first, that sounds like the obvious solution.
If a mutation is undesirable, why not immediately remove every carrier from breeding?
Because responsible breeding involves much more than one single gene.
A German Shepherd is the result of thousands of genes influencing:
• Temperament• Nerves• Working ability• Structure• Hips and elbows• Longevity• Immune function• Fertility• Movement• Size• Pigmentation• Breed type• And many other characteristics
If breeders aggressively removed every otherwise excellent dog simply because it carried one recessive mutation, they could unnecessarily shrink the gene pool and lose valuable genetic diversity.
This is not just a breeder’s opinion.
The OFA specifically cautions against over-emphasizing DM test results when making breeding decisions.
Its guidance explains that eliminating all carriers too aggressively can remove many high-quality dogs and may negatively affect the breed’s genetic diversity.
Instead, DM status should be considered alongside the dog’s other strengths and weaknesses.
That is an extremely important concept in responsible breeding.
Carrier Does Not Mean Sick
This deserves its own section because the word carrier is often misunderstood.
A DM carrier:
Does not have two copies of the risk mutation.
A carrier simply has the ability to pass one copy to approximately half of its puppies.
That is very different from a dog that is genetically at risk because it inherited two copies.
Think of it as carrying one piece of a two-piece puzzle.
If that dog is bred to a clear dog, the clear parent cannot provide the second mutation.
Therefore, the puppies cannot receive the two-copy combination associated with increased DM risk.
What Happens If Two DM Carriers Are Bred Together?
This is where the situation changes.
Carrier × Carrier
N/DM × N/DM
Statistically, the puppies could be approximately:
25% Clear — N/N
50% Carrier — N/DM
25% At Risk — DM/DM
UC Davis specifically notes that breeding two carriers is predicted to produce approximately 25% puppies with two copies of the DM-associated allele.
For that reason, responsible breeders can use DNA testing to avoid producing the high-risk genetic combination.
DM Testing Is a Tool — Not a Crystal Ball
The DM test is extremely useful.
But it is not perfect.
Researchers at the University of Missouri have documented dogs with clinical signs resembling DM that did not have two copies of the known SOD1 mutation.
This has been observed particularly in German Shepherd Dogs and suggests that other genes or neurologic diseases may sometimes produce similar symptoms.
At the same time, some dogs that test DM/DM never develop clinical disease.
So the DNA test tells us about genetic risk, not destiny.
The most accurate interpretation is:
Clear = very low genetic risk from the tested mutation.
Carrier = one copy, primarily important for breeding decisions.
At Risk = two copies and a substantially higher genetic risk, but not a guarantee that disease will develop.
DM Is Also a Diagnosis of Exclusion
Rear-leg weakness in an older German Shepherd does not automatically mean DM.
Other conditions can produce similar symptoms, including orthopedic and neurologic diseases.
Even UC Davis emphasizes that other, often more common and sometimes treatable causes of progressive rear-end weakness should still be investigated — even in dogs that genetically test DM/DM.
That is why veterinarians evaluate the entire dog rather than diagnosing DM from a cheek-swab result alone.
Should German Shepherd Puppy Buyers Worry About DM?
It is something they should understand.
And it is something responsible breeders should test for and manage.
But seeing the word:
Carrier
should not automatically cause panic.
A responsible breeder can safely incorporate a carrier into a breeding program by pairing that dog appropriately.
For example:
Clear × Carrier
is fundamentally different from:
Carrier × Carrier
The first mating cannot produce puppies with two copies of the tested mutation.
The second potentially can.
That distinction is far more important than simply asking:
“Is every parent DM clear?”
Responsible Breeding Is About Managing Genetics, Not Chasing Perfection
There is no genetically perfect German Shepherd.
Every dog carries countless genetic variations.
The goal of responsible breeding is not to pretend that every dog is genetically flawless.
The goal is to:
Know what you are breeding.
Test what can reasonably be tested.
Understand the inheritance.
Make breeding decisions that minimize risk while preserving the valuable qualities of the breed.
A wonderful German Shepherd with excellent temperament, structure, health, working ability and longevity does not suddenly become genetically worthless because it carries one copy of a recessive mutation.
Modern DNA testing actually gives breeders something previous generations did not have:
The ability to know the dog’s genetic status and choose the appropriate partner.
That is progress.
The Bottom Line on DM in German Shepherds
Degenerative Myelopathy is a serious disease.
It should never be ignored.
But DM genetics should also not be misunderstood.
DM Clear × DM Clear
Puppies are expected to be clear for the tested mutation.
DM Clear × DM Carrier
Puppies may be clear or carriers, but they are not expected to inherit two copies of the tested mutation.
DM Carrier × DM Carrier
There is a possibility of producing DM/DM puppies.
DM/DM
Means genetically at risk — not automatically clinically affected.
The OFA’s breeding guidance emphasizes that DM results should be used as one part of a balanced breeding program, rather than becoming the only factor used to determine whether an otherwise valuable dog should reproduce.
And perhaps that is the most important lesson of all:
Responsible breeding is not about eliminating every carrier.
It is about understanding genetics well enough to avoid producing preventable disease while maintaining the health, quality and genetic diversity of the German Shepherd Dog.
Learn More About Haus Neufus German Shepherds
At Haus Neufus German Shepherds, responsible breeding means looking at the entire dog — not simply one test result.
Health, temperament, structure, genetics, working ability and breed character all matter when making thoughtful breeding decisions.
Haus Neufus German ShepherdsDevoted to Family. Born to Protect.
