Hereditary necrotising myelopathy or ENM for short is a hereditary health condition that is also sometimes known as leukodystophy or Kooiker paralysis, and is found in the Kooikerhondje dog breed. The condition affects the dog’s spinal cord, leading to ultimate paralysis at a young age.

The condition leads to a progressive destruction of the dog’s spinal cord, which is not painful but is paralysing, and that ultimately eventually proves fatal in affected dogs.

Hereditary necrotising myelopathy usually becomes apparent in affected dogs while they are still young-usually during their first year of life-and begins with muscle weakness and changes in gait in the hind limbs, progressing via the spine to the front legs until the dog is completely paralysed, and the paralysis also affects the dog’s ability to breathe and so, leads to death by asphyxiation if allowed to progress naturally.

The condition is incurable, and affected dogs are usually euthanized once their quality of life begins to decline, to prevent further suffering.

Hereditary necrotising myelopathy is not contagious, and the only way it can be passed from dog to dog is by means of heredity, from parent dogs to their offspring. Dogs that carry the gene mutation for the condition pass on a copy of the defective gene to their offspring, and the status of both of the two parent dogs combined dictates whether or not their puppies will be affected with the condition themselves.

Because the condition is serious and incurable, The Kennel Club oversees a testing scheme for the condition, to allow potential breeders of dogs considered to be at risk of the condition to find out the status of their own dog before going ahead with breeding.

In this article, we will look at hereditary necrotising myelopathy in more detail, including how the heredity of the condition works, and how to get your dog tested. Read on to learn more.

More about hereditary necrotising myelopathy

Hereditary necrotising myelopathy is a progressive spinal condition that usually becomes evident in affected dogs between the ages of around twelve weeks and one year old, but can be as late as fifteen months. The earlies signs of the condition begin with an abnormal hind leg gait that causes the toes and nails to scuff and wear down, and then hind limb paralysis, followed by fore limb paralysis, and ultimately, an inability to move at all or breathe properly.

Few dogs affected with the condition live past the age of two, and are often euthanized much sooner to prevent suffering. There is no cure for the condition and while the spinal degeneration itself is not painful, the impact it has upon the dog’s quality of life is significant.

What sort of dogs can be affected by the condition?

Hereditary necrotising myelopathy is most prevalent in the Kooikerhondje dog breed, to the point that pre-breeding screening for dogs of the breed is strongly advised, and mandatory in the breed’s home country of the Netherlands.

Some other breeds are also known to be affected by the condition at a much lower degree of prevalence, and you can find out if your own dog’s breed is one of them by using The Kennel Club’s health results by breed checker tool.

In the Netherlands, where the highest concentration of Kooikerhondje dogs live, the gene mutation that causes the condition has been identified in around 25% of all dogs of the breed.

Dogs that have one Kooikerhondje parent may inherit one copy of the mutated gene from the Kooikerhondje side of their breed line too, but outcrossing to an unrelated breed makes it highly unlikely that a hybrid dog will be unlucky enough to inherit the affected form of the condition.

How does the heredity of the condition work?

Hereditary necrotising myelopathy is an autosomal recessive hereditary condition, which means that inheriting one copy of the gene mutation that causes the condition is not enough on its own to lead to the affected form for the condition.

Dogs are assigned one of three statuses for the condition: clear, carrier or affected.

• Two clear dogs will produce clear puppies.
• Two affected dogs will produce affected puppies.
• Two carriers will produce a mixture in their litter with each pup having odds of 50% carrier, 25% affected and 25% clear.
• A carrier and a clear dog will produce 50% carriers and 50% clear.
• A carrier and an affected dog will produce 50% carriers and 50% affected.
• A clear dog and an affected dog will produce a litter of carriers.

How to get your dog tested for hereditary necrotising myelopathy

In order to get your dog tested for hereditary necrotising myelopathy prior to breeding, you will need to send off a DNA sample from your dog (your vet can arrange this for you) to one of The Kennel Club’s approved laboratories, who will then return the status of your dog.