Golden Retriever Muscle Dystrophy (GRMD Dog)
Golden Retriever Muscle Dystrophy (GRMD) is a degenerative muscle disease in which muscle fibre degeneration and necrosis occur due to a malformation of the dystrophin protein. Affected dogs suffer from muscle wasting, weakness and feeding difficulties. The poor quality of life often leads to euthanasia.
The disease occurs in Golden Retrievers and is inherited in an X-linked recessive manner.
Synonym: X-linked muscular dystrophy, Duchenne muscular dystrophy, Dystrophin-deficient muscular dystrophy
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Symptoms
- "hopping-like" gait
- Loss of body coordination
- Crouched posture (due to curvature of the spine)
- Outward position of the forelimbs
- Difficulty with jaw movement, tongue progressively enlarges → leads to dysphagia (prevented food intake)
- Excessive salivation
- Progressive weakness and muscle wasting
- Degeneration of the entire skeletal musculature
General Information
- Muscular dystrophy (GRMD) is a degenerative muscle disease in which the muscle protein dystrophin is not produced.
- The lack of dystrophin protein leads to muscle fibre degeneration and necrosis.
- Symptoms begin at 6-10 weeks of age.
- Usually, more males than females are affected. However, GRMD-affected females are also known.
- Females are often misdiagnosed and GRMD remains undiagnosed for a long time.
- Poor quality of life often leads to euthanasia.
- The same disease occurs in humans: Duchenne muscular dystrophy (DMD).
Breeds affected
Golden Retriever
Test Information
This mutation test shows the change of a single base pair in exon 6 of the DMD gene.
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Also in the Golden Retriever B package (DRC P4)
In other breeds (e.g.: Labrador Retriever, Irish Terrier, Samoyed, Rottweiler, Tervuren, Miniature Schnauzer) other mutations have been found that lead to this disease. This test does not test for those mutations.
Genotype and Lab Report
Inheritance: X-linked recessive.
The affected gene is located on the X chromosome. Male dogs with this mutation are affected (X-grmd/Y). Females are affected if both X chromosomes are affected (X-grmd/X-grmd). They can also have one normal and one mutated chromosome and thus be asymptomatic carriers (X/X-grmd).
Genotypes:
X/X
The dog is a healthy female.
X/X-grmd
The dog is a carrier female. It is healthy, but can pass on 50% of the mutation (X-grmd) to the offspring.
X-grmd/X-grmd
The dog is an affected female and usually does not live long enough to reproduce.
X/Y
The dog is a healthy male.
X-grmd/Y
The dog is an affected male and usually does not live long enough to reproduce. If it does, 50% of the triggering mutation is passed on to the offspring (females). All female offspring are carriers.
Recommendations
- Carrier females (X/X-grmd) should not be used for breeding.
- Female offspring of a carrier female should be tested for their genotype (X/X or X/X-grmd).
- Affected animals should be excluded from breeding if they reach breeding age.
Literature
Sharp, N.J.H., Kornegay, J.N., Vancamp, S.D., Herbstreith, M.H., Secore, S.L., Kettle, S., Hung, W.Y., Constantinou, C.D., Dykstra, M.J., Roses, A.D., Bartlett, R.J. : An Error in Dystrophin Messenger RNA Processing in Golden Retriever Muscular Dystrophy, an Animal Homologue of Duchenne Muscular Dystrophy Genomics 13:115-121, 1992. Pubmed reference: 1577476.
Further information is available at: Online Mendelian Inheritance in Animals.