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Golden Retriever muscular dystrophy (GRMD) is an X-linked recessive inherited disease that causes progressive muscle degeneration, homologous to human Duchenne muscular dystrophy. It is characterised by progressive muscle weakness and atrophy with replacement of muscle by fatty and fibrous tissue, affecting skeletal and cardiac musculature.

It affects the Golden Retriever and has been documented in several countries. The carrier frequency is not firmly established in the verified sources.

- Progressive muscle weakness (proximal muscles)
- Difficulty climbing stairs, jumping or walking on uneven ground
- 'Bunny hopping' gait (jumping with both hind legs)
- Muscle atrophy (back, thighs)
- Exercise intolerance
- Dyspnoea due to weakness of intercostal muscles
- Dysphagia in advanced cases
- Cardiac changes (cardiomyopathy) and death from respiratory or cardiac failure

GRMD was recognised as the canine homologue of Duchenne muscular dystrophy and is the most widely used spontaneous animal model of this disease. Sharp and colleagues (1992) demonstrated that the cause is an error in dystrophin mRNA processing: a base change in the 3' consensus splice site of intron 6 causes skipping of exon 7 and disruption of the reading frame. The DMD gene encodes dystrophin, a structural protein critical for the integrity of the muscle fibre membrane.

- Test the breeding line (DMD genotyping) before the first mating
- Affected males must not be bred
- Carrier females should only be mated to non-carrier males
- Keep a genetic record in the pedigree
- Monitor cardiac and respiratory function in affected animals

The differential diagnosis includes mitochondrial myopathies, myasthenia gravis, polymyositis and other muscular dystrophies; the genetic test is definitive. There is no curative treatment: management is supportive (physiotherapy, nutritional support, cardiac and respiratory care). The prognosis is guarded, with survival usually of a few years in severe forms.

1. Sharp NJ, Kornegay JN, Van Camp SD, et al. An error in dystrophin mRNA processing in golden retriever muscular dystrophy, an animal homologue of Duchenne muscular dystrophy. Genomics. 1992;13(1):115-121. PMID: 1577476
2. Kornegay JN. The golden retriever model of Duchenne muscular dystrophy. Skelet Muscle. 2017;7(1):9. PMID: 28526070