Overview
Progressive retinal atrophy (PRA) is the most common form of inherited disease affecting the retina in dogs. Genetically different forms of PRA, caused by mutations in different genes, affect many breeds of dog with each form usually affecting one or a small number of breeds. PRA is characterised by progressive degeneration of the retina at the back of the eye and leads to vision loss and blindness.
This disease variant affects the Miniature Schnauzer. Age of onset is around 4 to 5 years old and clinical signs of disease onset are the dog having difficulty seeing at night in the first instance, which will progress to limited vision in the day to total blindness.
The deletion in the gene that causes Progressive Retinal Atrophy in Miniature Schnauzer is X-linked. Females that carry two copies of the variant (homozygotes) and males that carry one copy of the variant (hemizygotes) will almost certainly develop Progressive Retinal Atrophy during their lives. Females that carry a single copy of the mutation (also known as carriers or heterozygotes) will not develop Progressive Retinal Atrophy as a result of the variant, but they will pass the variant onto about half of any offspring they have.
Breeding dogs that will not develop Progressive Retinal Atrophy should be the breeder’s priority, with a reduction in variant frequency within the whole breed being the secondary, longer-term target.
Carriers should not be bred from, even if they are mated to a dog that has also been tested and is clear of the variant (i.e. carry no copies of the variant). If a carrier is mated to a clear dog approximately half of the resulting puppies will either be carriers if they are female or affected if they are male.
