-Degenerative Myelopathy (DM)-

A progressive spinal cord disease – meaning, symptoms and inheritance
Degenerative Myelopathy is a neurodegenerative disease of the spinal cord that occurs in older dogs and leads to a gradual paralysis of the hind legs. The gene responsible has also been identified in English Cocker Spaniels, although the disease is not common in this breed.
What happens in DM?
DM causes a gradual breakdown of nerves in the spinal cord, especially in the thoracic region. Symptoms usually appear between six and eight years of age, sometimes later.
Typical symptoms:

Unsteady, dragging gait of the hind legs
Sliding or scuffing of the paws
Weakness in the hindquarters and increasing mobility problems
In advanced stages: complete paralysis of the hind legs

The disease is incurable and can only be treated symptomatically. It is usually not painful.
Inheritance
DM is inherited in an autosomal recessive manner with incomplete penetrance. This means:

A dog must carry two copies of the mutated gene (homozygous affected) to develop the disease.
Carrier dogs (heterozygous) are healthy but can pass the gene on.
Not every dog with two defective genes will necessarily show symptoms — genetic predisposition is one factor, but environmental influences and other genes also play a role.

Genotype	Meaning	Health Status/Risk	Breeding Eligibility
N/N (clear)	The dog has tested clear of any defective genes	Will not develop the disease	Eligible for Unrestricted Breeding Use
N/DM (carrier)	The dog carries a only defective gene	Has a 50% chance of passing on the defective gene,	Carrier of a defective gene – mating only with an N/N (clear) partner
DM/DM (affected)	Genetic status: affected (two copies of the mutation)	Significantly increased risk of illness	Not approved for breeding.

VMating Charts – What Do They Show?
Mating charts help predict the genetic outcome of planned breedings. They show the likelihood of offspring being clear, carriers, or affected by inherited diseases based on the genetic status of both parents. This ensures responsible and health-focused breeding decisions.

Sire	Dam	Progeny
A (Clear)	A (Clear)	100 % Clear
A (Clear)	B (carrier)	50 % Clear, 50 % carrier
A (Clear)	C (affected)	100 % carrier
B (carrier)	B (carrier)	25 % frei, 50 % carrier, 25 % affected
B (carrier)	C (affected)	50 % carrier, 50 % affected
C (affected)	C (affected)	100 % affected

Since DM (Degenerative Myelopathy) can be identified through genetic testing, the birth of affected puppies can be reliably prevented. Responsible breeders test their dogs before breeding – even though DM is rare in English Cocker Spaniels.