Hypomyelinogenisis is a hereditary disorder that affects a dog's nerve cells. It's when their systems are not able to produce enough myelin which is fatty liquid and its job is to cover parts of nerve cells that transfer electrical impulses to other cells found in a dog's body. Myelin acts as an important insulator that protects nerves from any damage and when things go wrong it has a serious and negative impact on a dog's central nervous system.
It has been found that certain breeds are more at risk of inheriting the disorder than others and this includes the following breeds:
With Welsh Springer Spaniels as well as Samoyeds, it is male puppies that appear to be at greater risk of inheriting this congenital disorder with symptoms manifesting themselves very soon after a puppy is born. However, female puppies tend to be asymptomatic carriers of Hypomyelinogensis. In other breeds known to be more predisposed to inheriting the disorder, research has not established any gender specific differences. With this said, in Golden Retrievers, there is a higher rate of both females and males inheriting peripheral nervous system hypomyelination with puppies as young as eight weeks old showing symptoms of the condition.
Should a puppy have inherited the disorder it would typically affect their central nervous system with signs of there being a problem manifesting themselves within days of a puppy having been born. The symptoms they display are as follows:
Tremors - these worsen when puppies are active. The tremors are far less obvious when puppies are resting
Symptoms typically improve when dogs are around twelve months old. However, in Welsh Springer Spaniels as well as Samoyeds, the symptoms remain with them for the rest of their lives. When a dog's peripheral nervous system is affected, the signs of there being a problem start to manifest themselves when puppies are anything from 5 to 7 weeks old and the signs of there being a problem include the following:
Research has shown that a recessive gene is responsible for the condition in Welsh Springer Spaniels. However, just why other breeds are more predisposed to inheriting Hypomyelinogenisis remains unknown. With this said, there is some thought that toxic or viral sources would be responsible, more especially as in certain instances a dog's condition gets better as time passes and they mature. Where peripheral nervous system disease is the problem, vets do not as yet know why some breeds are affected whereas others are not, but there is a strong suspicion of there being a genetic link.
A vet would need to have a dog's full medical history and they would ideally need to know their lineage too. Vets would then carry out a full physical examination of a dog suspected of suffering from Hypomyelinogenisis. The sort of tests they would want to carry out include the following:
A vet would study all clinical signs to diagnose the condition. However, to establish whether a dog is suffering from Hypomyelinogenisis, they would need to take a biopsy of the nerve to see if there is enough myelin present at its axon. It may also be necessary to carry out a brain biopsy on a dog, but there are other tests that would determine whether a dog has the condition or not which includes establishing whether their motor and sensory nerves are working correctly.
Sadly, for the moment, there is no treatment available for dogs suffering with Hypomyelinogenisis whether its peripheral or central.
Dogs with the condition should not be used in a breeding programme. However, the symptoms they display when suffering from the disorder generally start to improve as they reach twelve months old. In Welsh Springer Spaniels as well as Samoyeds, their symptoms remain present for the rest of a dog's life. If a dog is diagnosed as suffering from peripheral nervous system hypomyelination, they usually go on to lead full and happy lives.