Disease overview

Autosomal Dominant Progressive Retinal Atrophy (AD-PRA) causes breakdown of the retina, which is a part of the eye essential for vision. This eye disease affects both types of photoreceptors: rods and cones. Rods are essential for night vision and movement, while cones are used for day vision and color. AD-PRA is a progressive disease that is non-painful. Studies have identified English Mastiff dogs with a naturally occurring dominant retinal degeneration and determined that the cause is a point mutation in the RHO gene (G>C; Thr4Arg). Dogs with this mutant allele exhibit a retinal phenotype that closely mimics the trait in humans with RHO mutations.

Gene name

RHO

Inheritance

Autosomal dominant

Signs and symptoms

Though signs of AD-PRA can develop as early as 8 weeks of age, they are often easily missed until an affected dog is 2-3 years old and symptoms become more pronounced. Signs include night blindness, nervousness at night, reluctance to go into dark areas of the house, general clumsiness or bumping into furniture and corners in low light conditions. PRA is generally a progressive disease where loss of vision occurs over time (allowing a dog to adapt more easily) before complete blindness sets in. This autosomal dominant form of PRA, however, can be triggered by exposure to high intensity light, leading to a rapid decline in vision within 2 weeks to a month and ultimately resulting in blindness.

How is it diagnosed

A veterinarian will conduct a thorough examination of the pupils and the retina. Depending on the outcome of the exam, they may provide a referral to a veterinary ophthalmologist to confirm an AD-PRA diagnosis. Genetic testing to detect mutations in the RHO gene assists veterinarians with diagnosis and helps breeders identify affected and carrier dogs.

Breeds at higher risk

English Mastiff,

Citations

Kijas JW, Cideciyan AV, Aleman TS, Pianta MJ, Pearce-Kelling SE, Miller BJ, Jacobson SG, Aguirre GD, Acland GM. Naturally occurring rhodopsin mutation in the dog causes retinal dysfunction and degeneration mimicking human dominant retinitis pigmentosa. Proc Natl Acad Sci U S A. 2002 Apr 30;99(9):6328-33. doi: 10.1073/pnas.082714499. Epub 2002 Apr 23. PMID: 11972042; PMCID: PMC122948.

Cideciyan AV, Jacobson SG, Aleman TS, Gu D, Pearce-Kelling SE, Sumaroka A, Acland GM, Aguirre GD. In vivo dynamics of retinal injury and repair in the rhodopsin mutant dog model of human retinitis pigmentosa. Proc Natl Acad Sci U S A. 2005 Apr 5;102(14):5233-8. doi: 10.1073/pnas.0408892102. Epub 2005 Mar 22. PMID: 15784735; PMCID: PMC555975.

Disclaimer

Disease diagnosis and treatment should always be performed by a veterinarian. The following information is for educational purposes only.