Progressive Retinal Atrophy, PRA4 (Lhasa Apso Type)

General Information: Progressive Retinal Atrophy (PRA4) in Lhasa Apsos manifests as a gradual loss of vision, starting with night blindness due to the early degeneration of rod cells responsible for low-light vision. As the disease progresses, cone cells, which facilitate daylight and color vision, also deteriorate, leading to a broad loss of sight. Initial symptoms include poor vision in dim lighting and a loss of peripheral vision, which gradually extends to difficulties in bright light conditions. Veterinary eye exams may reveal changes in the eye's internal reflectivity, particularly in the tapetum—a layer behind the retina that aids in night vision. The onset of symptoms is often subtle, and the condition may not be noticeable until significant vision impairment occurs.

How to Read Your Dog's Test Results for this Genetic Variant:

Two Variants Detected: Dog Likely Affected

One Variant Detected: Dog Unlikely Affected

No Variants Detected: No Effect

Gene / Testing Information: Genetic testing for Progressive Retinal Atrophy (PRA4) in Lhasa Apsos targets mutations in the IMPG2 gene, which is crucial for diagnosing this specific form of progressive retinal atrophy. The disease is inherited in an autosomal recessive pattern, meaning that a dog must inherit two copies of the mutated gene—one from each parent—to exhibit symptoms of PRA4. Dogs with one mutated gene (carriers) do not typically show symptoms but can pass the mutation on to their offspring. Breeding two carriers results in a 25% chance of producing affected offspring and a 50% chance of producing another carrier. To prevent the spread of this condition, it is advised against breeding carriers together. Genetic testing before breeding is essential to identify carriers and manage breeding decisions effectively, aiming to reduce or eliminate this debilitating gene mutation from the Lhasa Apso population.