Paradoxical pseudomyotonia in English Cocker Spaniels and English Springer Spaniels

Myotonia is generally characterized by persistent muscle contraction and slowed relaxation. Dogs affected by paradoxical pseudomyotonia experience episodes of muscle stiffness after strenuous physical activity (stair walking, jumping, fast running), which may be accompanied by cyanosis (bluing of mucous membranes and skin) and apnoea (respiratory arrest). The extreme outdoor temperatures seemed to considerably worsen episode frequency and severity in most dogs. Clinical signs usually first appear before the age of 2 years.

The disease is caused by a nonsense mutation c.126C>A in the SLC7A10 gene.

The mode of inheritance of the mutation is autosomal recessive. This means that only individuals who inherit the mutated gene from both parents will develop the disease. Carriers of the mutated gene are clinically healthy but pass the mutation on to their offspring. In the case of a mating between two heterozygous individuals, theoretically 25% of the offspring will be completely healthy, 50% of the offspring will be carriers and 25% of the offspring will inherit the mutated gene from both parents and will therefore be affected by the disease.

The genetic test can clearly reveal the genotype of the animal and is a useful tool for breeders to prevent unintentional breeding of affected puppies.

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Reference:

Van Poucke, M., Stee, K., Lowrie, M., Peelman, L. : The c.126C>A(p.(Cys42Ter)) SLC7A10 nonsense variant is a candidate causative variant for paradoxical pseudomyotonia in English Cocker and Springer Spaniels. Anim Genet , 2023. Pubmed reference: 36869603