Common Symptoms
Acral mutilation syndrome is an inherited neurological disease affecting dogs. Affected dogs present around 4 months of age with an insensitivity to pain in the lower limbs demonstrated by repetitive licking and biting of their paws, eventually resulting in self-mutilation. Affected dogs are often smaller than littermates and present with severe, self-induced wounds of the feet including toe amputations, toenail loss, and bone fractures. Dogs with open wounds are subject to additional complications from secondary infections. Since affected dogs are unable to feel pain in their feet, they will continue to walk without obvious discomfort. Euthanasia is often requested by owners due to quality of life concerns and a lack of treatment options.
Breed-Specific Information for the Cocker Spaniel
Cocker spaniel is included as a breed susceptible to acral mutilation syndrome because of its close relatedness to the English cocker spaniel breed, which has been identified in the Paw Print Genetics laboratory to carry the GDNF Mutation associated with this disease. Neither the frequency of the causal mutation nor its association with disease in this breed has been reported in the medical literature. In addition, multiple apparently healthy English cocker spaniels with two copies of the GDNF mutation have been identified by Paw Print Genetics. Thus, suggesting that this disease may display Incomplete Penetrance in this breed.
Testing Tips
Genetic testing of the GDNF gene in cocker spaniels will reliably determine whether a dog is a genetic Carrier of acral mutilation syndrome. Acral mutilation syndrome is inherited in an Autosomal Recessive manner, meaning that dogs must receive two copies of the mutated gene (one from each parent) to be at an increased risk of developing disease. Paw Print Genetics has identified multiple apparently healthy dogs with two copies of the GDNF Mutation (including old English sheepdogs and English cocker spaniels). Therefore, acral mutilation syndrome may display Incomplete Penetrance, meaning that some dogs which inherit two copies of the GDNF mutation may not develop this disease. In general, carrier dogs do not have features of the disease but when bred with another carrier of the same Mutation, there is a risk of having affected pups. Each pup that is born to this pairing has a 25% chance of inheriting two copies of the mutation (at risk for disease) and a 50% chance of inheriting one copy and being a carrier of the GDNF gene mutation. Reliable genetic testing is important for determining breeding practices. Because the mutation may display incomplete Penetrance, genetic testing should be performed before breeding. In order to eliminate this mutation from breeding lines and to avoid the potential of producing affected pups, breeding of known carriers to each other is not recommended. Cocker spaniels that are not carriers of the mutation have no increased risk of having affected pups.
There may be other causes of this condition in dogs and a normal result does not exclude a different mutation in this gene or any other gene that may result in a similar genetic disease or trait.
References
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Cummingss JF, de Lahunta A, Winn SS. Acral mutilation and nociceptive loss in English pointer dogs. A canine sensory neuropathy. Acta Neuropathol. 1981;53(2):119-27.
[PubMed: 6259871]
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Plassais J, Lagoutte L, Correard S, Paradis M, Guaguere E, Hedan B, Pommier A, Botherel N, Cadiergues M, Pilorge P, Silversides D, Bizot M, Samuels M, Arnan C, Johnson R, Hitte C, Salbert G, Mereau A, Quignon P, Derrien T, Andre C. A Point Mutation in a lincRNA Upstream of GDNF Is Associated to a Canine Insensitivity to Pain: A Spontaneous Model for Human Sensory Neuropathies. PLoS Genet. 2016 Dec 29;12(12):e1006482.
[PubMed: 28033318]
