Health Screening Guide
DM in French Bulldogs
Degenerative Myelopathy explained: what it is, how it is inherited, how to test for it, and how responsible breeders avoid producing affected puppies.
Check Your PairingWhat Is Degenerative Myelopathy?
Degenerative Myelopathy (DM) is a devastating progressive disease that attacks the white matter of the spinal cord. It begins with subtle weakness in the hind legs and gradually advances to complete paralysis. There is no cure, and affected dogs eventually lose control of all four limbs.
In French Bulldogs, DM is caused by a single mutation in the SOD1 gene. Because it is recessive, a dog must inherit two mutated copies — one from each parent — to develop the disease. Dogs with only one copy are carriers: they live normal, healthy lives but can pass the mutation on.
Symptoms typically appear between 8 and 14 years of age, which is why genetic testing is critical before breeding. You cannot tell by looking at a dog whether it carries DM. Only a DNA test reveals the genotype.
How DM Is Inherited
DM follows simple Mendelian recessive inheritance. Here is what happens when you pair dogs with different DM genotypes.
N / NClearNo DM mutation present. Cannot produce affected or carrier puppies.
N / DMCarrierCarries one mutated copy. Healthy, but can pass DM to 50% of offspring.
DM / DMAffectedTwo mutated copies. Will eventually develop DM. Should never be bred.
The Golden Rule
Never breed two carriers (N/DM x N/DM) together. This pairing produces a 25% chance of affected puppies (DM/DM), a 50% chance of carriers, and only a 25% chance of clear puppies. Our DNA Calculator flags this automatically.
Safe vs. Risky DM Pairings
N/N x N/NThe safest pairing. All puppies are clear.
0% affected, 0% carriers
N/N x N/DMSafe to breed. No affected puppies, but some carriers produced.
0% affected, 50% carriers
N/N x DM/DMAll puppies will be carriers. No affected puppies, but every pup carries the gene.
0% affected, 100% carriers
N/DM x N/DMDangerous pairing. One in four puppies will be affected with DM.
25% affected, 50% carriers, 25% clear
N/DM x DM/DMNever breed this combination. Half the litter will develop DM.
50% affected, 50% carriers
DM/DM x DM/DMAbsolutely prohibited. Every puppy will be affected.
100% affected
Screen Your Frenchies Before Breeding
Our free DNA Calculator checks every health gene including DM, HUU, JHC, and CMR1. Enter your dogs' genotypes and see exactly which risks your pairing produces.
Open the DNA CalculatorFrequently Asked Questions
What is Degenerative Myelopathy (DM) in French Bulldogs?
Degenerative Myelopathy (DM) is a progressive, incurable spinal cord disease that affects older dogs. It is caused by a mutation in the SOD1 gene and leads to gradual paralysis starting in the hind legs. French Bulldogs that are affected (DM/DM) typically show symptoms between 8 and 14 years of age.
How is DM inherited in French Bulldogs?
DM is an autosomal recessive trait. A dog must inherit two copies of the mutated gene (DM/DM) to be affected. Dogs with one copy (N/DM) are carriers — they appear completely healthy but can pass the mutation to their offspring. Dogs with two normal copies (N/N) are clear and cannot produce affected puppies.
Should I breed a Frenchie that is a DM carrier?
Yes, carriers can be bred safely — but only to a clear (N/N) partner. When an N/DM dog is bred to an N/N dog, 50% of the puppies will be carriers and 50% will be clear. No puppy will be affected. Never breed two carriers together, as that produces a 25% chance of affected puppies.
What DNA test should I use for DM screening?
Use a reputable DNA testing service like Embark, Animal Genetics, or DDC. Request the full health panel, which includes the SOD1 gene test for DM. Results typically return within 2 to 4 weeks and provide a genotype for each locus.
Can DM be treated or cured?
There is currently no cure for Degenerative Myelopathy. Treatment focuses on slowing progression and maintaining quality of life through physical therapy, mobility aids, and pain management. Genetic testing before breeding is the only way to prevent producing affected puppies.
How do I use the DNA Calculator to avoid DM in my litter?
Enter the DM genotypes of both parents into our DNA Calculator. If either dog is affected (DM/DM) or both are carriers (N/DM), the calculator will flag the pairing and show you the exact risk percentages. Adjust your breeding plan to ensure no affected puppies are produced.