Progressive Retinal Atrophy

Progressive Retinal Atrophy (PRA) is a common term used for a group of inherited retinal disease. It degenerate the retina of the eye over time, eventually leading to blindness. This condition affects both eyes, and is not painful for the dog. In typical PRA rod photoreceptor responses are lost first followed by cone photoreceptor responses. It is seen in many breeds of dogs and very rarely in cats. It is similar to retinitis pigmentosa (RP) in human. RP is transmitted in different modes—autosomal dominant, autosomal recessive, X-linked, and digenic—as well as maternally ). PRA show several modes of transmission and a large number of genes and mutations are involved. Age-at-onset and rate of progression of disease differs between breeds. Some breeds experience an earlier onset than others and other breeds do not develop PRA until later in life. …show more content…
The retinas of dogs with PRA either have arrested development (retinal dysplasia) or early degeneration of the photoreceptors. Retinal dysplastic dogs are usually affected within two months of birth and may be completely blind by one year. Dogs with retinal degeneration are affected from one year to eight years of age and the symptoms progress slowly. With time PRA become worsens. Each PRA disease generally occurs in only one or a few breeds, as demonstrated for PRA with a known genetic basis. PRA-prcd is a notable exception, affecting more than 20 breeds. The first described case of PRA in dogs were in the early twentieth century and today more than 100 breeds have had cases of retinal degeneration. At least 22 mutations in 19 genes have been identified to be associated with different forms of PRA in more than 50 breeds. The mutations causing PRA in several breeds of dogs remain