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Summary
Leukodystrophies comprise a rare class of inherited nervous system diseases in which the protective covering of the peripheral nerves progressively loses an essential fatty protein called myelin. These so-called “demyelinating” diseases most often manifest as progressive weakness and difficulty walking––usually in young dogs, though cats have been known to be affected as well.
A wide variety of these diseases exists and most tend to be highly breed specific. One significant variation from most includes a leukodystrophy disease called globoid cell leukodystrophy. This version of leukodystrophy differs from the others in that the cause of the problem has been specifically identified as a disruption in myelin production due to the inherited deficiency of a certain enzyme.
For all kinds of leukodystrophies in which the mode of inheritance has been determined (including that of globoid cell leukodystrophy), the pattern has been identified as autosomal recessive.
Symptoms and Identification
These will vary according to the leukodystrophy variant and breed but can begin in dogs as early as two weeks of age and will progress slowly or rapidly from weakness to loss of coordination, abnormal gait and eventual paralysis in a great many cases. Again, however, the signs will vary according to the specific kind of leukodystrophy inherited.
Diagnosis of the condition is not straightforward given that the rarity of the disease renders its identification elusive. Normally, veterinary neurologists are enlisted to help with MRIs, nerve conduction studies and other helpful approaches to rule out diseases with similar symptoms. MRIs will be most helpful in determining whether the characteristic demyelination has taken place. Nerve sheath biopsy may also be helpful.
In the case of globoid cell leukodystrophy, a specific test is available to determine whether the disease has been inherited.
Affected Breeds
For globoid cell leukodystrophy, Cairn and West Highland White Terriers are the only breeds known to be affected.
Rottweiler leukodystrophy (also called leukoencephalomyelopathy) affects Rottweilers alone.
Dalmatian leukodystrophy happens only in the Dalmatian.
Miniature Poodle leukodystrophy (also called demyelinating myelopathy) is strictly seen in Miniature Poodles.
Hereditary ataxia (AKA, progressive ataxia) is a disease of Smooth-haired Fox Terriers and Jack Russell Terriers.
Hound ataxia is reported in Beagles, Fox Hounds, and Harrier Hounds.
Labrador Retriever central axonopathy is seen only in Labs.
Afghan myelomalacia is seen only in Afghan Hounds.
Spongiform leukodystrophy is peculiar to Labrador Retrievers, Samoyeds, and Silky Terriers.
Fibrinoid leukodystrophy (also called Alexander's disease) is a disease of Labrador Retrievers and Bernese Mountain Dogs.
Treatment
There is no known treatment for this class of diseases.
Veterinary Cost
The cost of diagnosis can be significant given the need for expensive imaging equipment and the heavy reliance on neurologist consultation.
Prevention
Because most dogs inherit this condition as an autosomal recessive trait, all affected dogs and their first degree relatives must be removed from the breeding pool. For globoid cell leukodystrophy, blood testing will help identify not only affected dogs but the carrier state as well, thereby aiding breeders in weeding out this trait through appropriate breeding.
References
OFA
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.