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Cone degeneration (German Shorthaired Pointer type) is an inherited eye disease affecting dogs. Affected dogs develop day-blindness (blindness in bright light) and Photophobia (light sensitivity) between 8 to 12 weeks after birth due to degeneration of cells in the eye called cone photoreceptors which are responsible for vision in bright light. Affected dogs have normal vision in low light and structures of the inner eye appear normal on a veterinary eye exam. Normal cone cell function can be seen on Electroretinogram (ERG) before six weeks of age, but becomes abnormal between 6 to 12 weeks of age and is completely absent in affected adult dogs signifying complete loss of Cone Cells. The cells responsible for vision in low light called Rod photoreceptors are not affected and thus, affected dogs will still be able to see normally in low light throughout life.
Acral Mutilation Syndrome
Pain Insensitivity, Sensory Neuropathy, AMS, SN
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 and 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, loss of toenails, and bone fractures. Dogs with open wounds are subject to additional complications associated with 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.
Genetic testing of the GDNF gene will reliably determine whether a dog is a genetic Carrier of acral mutilation syndrome. Acral mutilation syndrome is inherited in an Autosomal Recessive manner in dogs meaning that they must receive two copies of the mutated gene (one from each parent) to develop the 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 the 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. 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. Dogs 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.
- 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]
- 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]