Progressive Retinal Atrophy - PRA
What is Progressive Retinal Atrophy (PRA)?
Progressive Retinal Atrophy (PRA-CRX) or PRA is a group of degenerative diseases that affect these photoreceptor cells. With this disease, the cells deteriorate over time, eventually leading to blindness in the affected cat.
How is PRA inherited?
This is an autosomal recessive condition, meaning two copies of the mutation are required for the cats to lose their vision. Dam and sire must both be carreirs to produce affected offspring. Carriers have one copy of the mutation. Carriers are not affected and have normal vision.
PRA Symptoms
Dilated pupils
Inability to see clearly in bright light
In some conditions, only central vision may be lost and the cat may still retain peripheral vision
The pupil (opening of the eye) has abnormal reactions to light
The retinal structure appears abnormal when a doctor examines it with an ophthalmoscope; cataract may be observed
The liver may also be affected, obesity may be observed
What is the retina?
The retina is the tissue that lines the inner surface of the eye, and is the light sensitive part of the eye that acts as the brain's camera, transmitting images through the rods and cones that are part of its structure, thus enabling the experience of vision. The retina is part of the central nervous system (CNS) and the only part of the CNS that can be easily imaged and examined. In retinal degeneration, the cells of the retina begin to decline in function, thereby leading to impaired vision or even blindness. There are many causes for retinal degeneration.
PRA Genetic Testing
A single nucleotide mutation in the gene called CEP290 produces a defective protein which is associated with this progressive retinal atrophy (PRA) in the cat. In addition to Abyssinian, Somali and Ocicat, a survey of 43 cat breeds showed presence of the CEP290 mutation in many other breeds including, American Curl, American Wirehair, Bengal, Balinese/Javanese, Colorpoint Shorthair, Cornish Rex, Munchkin, Oriental Shorthair, Peterbald, Siamese, Singapura and Tonkinese. The high frequency of the CEP290 mutation in Siamese (about 33%) and related breeds (Oriental Shorthair, Balinese/Javanese, Colorpoint Shorthair, Peterbald) poses a significant health risk in the Siamese breed group.
| Test Result | CEP290 PRA-rdAc Status |
|---|---|
| N/N | Normal, cat does not have rdAc mutation* |
| N/rdAc | Carrier, cat has one copy of rdAc mutation. Breedings between carriers will be expected to produce 25% affected kittens. |
| rdAc/rdAc | Affected |