Progressive Retinal Atrophy Progressive Rod-Cone Degeneration
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Breeds: Akita, Akita Inu, American Hairless Terrier, American Morkshire Terrier, Aussiedoodle, Australian Cattle Dog, Australian Labradoodle, Australian Mix, Australian Mountain Doodle, Australian Shepherd, Australian Shepherd/Border Collie, Australian Stumpy Tail Cattle Dog, Basset Hound, Bernalier, Bernedoodle, Biewer Terrier, Bolognese, Bordoodle, Bracco Italiano, Braque d'Auvergne, British Labrador Retriever, Cavachon, Cavalier King Charles Spaniel, Cavapoo, Chesapeake Bay Retriever, Chihuahua, Chinese Crested, Clumberdoodle, Cockapoo, Cocker Spaniel, Corgipoo, Coton De Tulear, Dogue de Bordeaux, Double Doodle, English Cocker Spaniel, English Shepherd, Entlebucher Mountain Dog, Finnish Lapphund, Fox Terrier, Giant Schnauzer, Goldadoodlier, Goldador, Goldalier, Golden Retriever, Goldendoodle, Gordon Setter, Havanese, Hungarian Wirehaired Vizsla, Imperial Shih Tzu, Jack Russell Terrier, King Charles Bernedoodle, Labradoodle, Labrador Retriever, Lowchen, Maltipoo, Miniature American Shepherd, Miniature Australian Shepherd, Miniature Bernedoodle, Miniature Golden Retriever, Miniature Goldendoodle, Miniature Poodle, Miniature Schnauzer, Mixed Breed, Mixed Breed (Dog), Newfypoo, Norwegian Elkhound, Nova Scotia Duck Tolling Retriever, Parson Russell Terrier, Peruvian Inca Orchid, Poochon, Poodle, Portuguese Podengo Pequeno, Pudelpointer, Puli, Rat Terrier, Russell Terrier, Russian Tsvetnaya Bolonka, Saint Berdoodle, Schipperke, Schnoodle, Scotch Collie, Sheepadoodle, Shih Tzu, Silky Terrier, Spanish Water Dog, Standard Poodle, Standard Schnauzer, Toy Australian Shepherd, Toy Poodle, Unspecified, Unspecified Breed, Vizsla, Volpino Italiano, Whoodle, Wire Fox Terrier, Wirehaired Vizsla, Yorkiepoo, Yorkshire Terrier
Description
Progressive Rod-Cone Degeneration, or PRA-prcd, is a form of Progressive Retinal Atrophy (PRA) in which the cells in the dog's retina in the eye degenerate and die. PRA for dogs is similar to Retinitis Pigmentosa in humans. Most affected dogs will not show signs of vision loss until 3-5 years of age. Complete blindness can occur in older dogs. Progressive Rod-Cone Degeneration is a form of PRA known to affect over 40 different breeds.
The retina is a membrane located in the back of the eye that contains two types of photoreceptor cells. These cells take light coming into the eyes and relay it back to the brain as electrical impulses. These impulses are interpreted by the brain to "create" images. In dogs suffering from PRA-prcd, the photoreceptor cells begin to degenerate, causing an inability to see changes in light. This results in a loss of vision. Rod cells, which normally function in low-light or nighttime conditions, begin to degenerate first. This leads to night-blindness. The cone cells, which normally function in bright-light or daytime conditions, will deteriorate next. This often leads to complete blindness over a period of time.
PRA-prcd is inherited as an autosomal recessive disorder. Autosomal recessive disorders are disorders that can be passed from either parent and require two copies of the gene to show symptoms. A dog must have two copies of the mutated gene to be affected by PRA. A dog can have one copy of the mutation and not experience any symptoms of the disease. Dogs with one copy of the mutation are known as carriers, meaning that they can pass on the mutation to their offspring. If they breed with another carrier, there is a 25% chance that the offspring can inherit one copy of the mutated gene from each parent, and be affected by the disease.
Possible Results
| Genotype | Description |
|---|---|
| P/P | Affected: Dog has two copies of the prcd-PRA mutation. Dog will develop prcd-PRA and will always pass on a copy of the mutation to offspring. |
| n/P | Carrier: Dog is a carrier of the PRA-prcd mutation. Dog will not be affected by PRA-prcd but may pass the mutation to offspring. |
| n/n | Negative: Dog is negative for the mutation associated with prcd-PRA. |
Reference
Moody JA, Famula TR, Sampson RC, Murphy KE. Identification of microsatellite markers linked progressive retinal atrophy in American Eskimo Dogs. Am J Vet Res. 2005 Nov;66(11):1900-2. [PubMed: 16334947]
Zangerl B, Goldstein O, Philp AR, Lindauer SJ, Pearce-Kelling SE, Mullins RF, Graphodatsky AS, Ripoll D, Felix JS, Stone EM, Acland GM, Aguirre GD. Identical mutation in a novel retinal gene causes progressive rod-cone degeneration in dogs and retinitis pigmentosa in humans. Genomics. 2006 Nov; 88(5):551-63. [PubMed: 16938425]