Inherited Myopathy in Great Danes

Inherited Myopathy in Great Danes (IMGD) is a rare inherited degenerative muscle disorder. The affected dogs typically have an onset of symptoms between 3 and 6 months of age. The first signs include exercise intolerance, weakness and tremors. Frequent signs are overall stiff gait and short stride. In the progressive stage of the disease, the exercise results in exhaustion to the point of collapse. The clinical signs get worse under load, stress and low temperatures.

The severity of symptoms and the progression rate are variable and that even among the littermates. Most dogs are recommended for euthanasia due to overall exhaustion before one year of age. In some dogs a milder form of the disease without significant progression of symptoms was described.

The disease is caused by substitution IVS10-2A>G in the gene BIN1. The BIN1-gene encodes the protein Amphiphysin 2 that is necessary for the correct function of muscle fibres (Bőhm et al., 2013).

Mutation that causes IMDG in Great Danes is inherited as an autosomal recessive trait. That means the disease affects dogs with P/P (positive / positive) genotype only. The dogs with P/N (positive /negative) genotype are clinically without any symptom. They are genetically considered carriers of the disease (heterozygotes). In offspring of two heterozygous animals following genotype distribution can be expected: 25 % N/N (healthy non-carriers), 25 % P/P (affected), and 50 % N/P (healthy carriers).

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References:

Bőhm J, Vasli N, Maurer M, Cowling B, Shelton GD, et al. (2013) Altered Splicing of the BIN1 Muscle-Specific Exon in Humans and Dogs with Highly Progressive Centronuclear Myopathy. PLoS Genet 9(6): e1003430. doi:10.1371/journal.pgen.1003430