Leukodystrophies

What is ... ?: 

 In these rare conditions, there is gradual or rapid loss of myelin in the white matter tracts in the nervous system (brain and/or spinal cord). Myelin, a fatty substance that coats nerve cells, serves as an electrical insulator and is crucial to the normal conduction of nerve impulses.

Dogs affected by leukodystrophies show a loss of coordination (ataxia) reflected by difficulty in maintaining their balance, an irregular gait which may also be exaggerated (eg. high-stepping), and a progressive weakness. The conditions vary between breeds (depending on the specific changes in the white matter), and the differences are described below.
 
Some related terms and specific leukodystrophies are Afghan myelomalacia, Dalmatian leukodystrophy, degenerative myelopathy, fibrinoid leukodystrophy/ Alexander's disease, hereditary ataxia, hound ataxia, Labrador retriever central axonopathy, miniature poodle demyelinating myelopathy, myelomalacia, Rottweiler leukodystrophy, spongiform leukodystrophy.

How is ... inherited?: 

Dalmatian leukodystrophy, Rottweiler leukodystrophy, hereditary ataxia, Labrador retriever central axonopathy, and Afghan myelomalacia are believed to be autosomal recessive.

What does ... mean to your dog & you?: 

 Rottweiler leukodystrophy/ Leukoencephalomyelopathy: Affected dogs begin to lose muscle coordination (develop ataxia), somewhere between 11/2 to 4 years of age. They may also have an exaggerated gait. The condition worsens over 6 to 12 months until the dog is unable to rise.

Dalmatian leukodystrophy: Clinical signs of this disorder begin at 3 to 6 months of age, and include difficulties with vision, poor coordination, and weakness.
Miniature poodle leukodystrophy/ Demyelinating myelopathy: Signs of weakness begin at 2 to 4 months of age and rapidly worsen to paralysis.
Hereditary ataxia (progressive ataxia): This is seen in smooth-haired fox terriers and Jack Russell terriers. A gradual loss of coordination begins by 2 to 6 months of age, and progresses to the point where the dog is unable to walk. These dogs have what is called intention tremor - that is the tremor worsens with effort (to move toward something for example) and subsides when the dog is at rest.
Hound ataxia:This condition (seen in beagles, fox hounds, and harrier hounds) begins at 2 to 7 years of age with poor coordination in the hind limbs, which gradually worsens over the next 18 months or so. There is some evidence that this problem is due to environmental causes rather than of a hereditary nature.
Labrador retriever central axonopathy: Signs are evident by 4 to 6 weeks of age, and include lack of coordination, weakness and an exaggerated gait. By 5 months of age, affected pups are unable to walk.
Afghan myelomalacia (hereditary myelopathy of Afghan hounds): Signs of weakness and incoordination develop in affected dogs by 3 to 13 months of age and progress rapidly.
Spongiform leukodystrophy: Clinical signs start as early as 2 weeks of age and include tremors, lack of coordination and an exaggerated gait. This condition has been reported in Labrador retrievers, samoyeds, and silky terriers.
Fibrinoid leukodystrophy/ Alexander's disease: This very rare condition has been reported in Labrador retrievers and Bernese mountain dogs. Signs associated with loss of myelin appear by 6 to 9 months of age.

How is ... diagnosed?: 

 These conditions are rare. Your veterinarian will base the diagnosis on the clinical signs, a detailed neurological examination, and lack of abnormalities on other diagnostic tests. The specific changes in the nervous system can only be confirmed by examination after death (post-mortem examination).

How is ... treated?: 

 Unfortunately there is no treatment for these disorders. Your veterinarian will help you decide when your dog's condition has deteriorated to the point where euthanasia is the best option. 

For the veterinarian: 

 Clinical signs reflect progressive demyelination in white matter tracts, which may be in the cerebrum, cerebellum, brainstem, cranial nerves,and/or spinal cord, depending on the specific condition in the affected breed. Generally there is ataxia and upper motor neuron para/tetraparesis which progresses to para/tetraplegia.

Breeding advice: 

 Except in the rottweiler, the signs of these conditions are apparent before breeding age. Of course affected dogs should not be used for breeding; breeding of parents and siblings (suspect carriers) should be avoided as well.

FOR MORE INFORMATION ABOUT THIS DISORDER, PLEASE SEE YOUR VETERINARIAN.

Resources: 

 Ackerman, L. 1999. The Genetic Condition: A Guide to Health Problems in Purebred Dogs. pp 137-138. AAHA Press. Lakewood, Colorado.

 LeCouteur, R.A., Child, G. 1995. Diseases of the spinal cord. In S.J. Ettinger and E.C. Feldman (eds.) Textbook of Veterinary Internal Medicine, p. 629-696. W.B. Saunders Co., Toronto.


What breeds are affected by ... ?
Tags: