Progressive Retinal Atrophy B Type 1 (PRA-B1)

Progressive retinal atrophy (PRA) in dogs is a group of genetically heterogeneous inherited retinal disorders characterized by progressive retinal degeneration and photoreceptor cell death. PRA affects over hundred dog breeds. Currently more than twenty variants in nineteen genes were associated with the disease. Clinical findings in PRA include gradual loss of vision, and attenuation of the retinal blood vessels, which result from the degeneration of the photoreceptor layer in the retina.

In Miniature Schnauzers there are several forms of PRA differing in the age of onset and sex prevalence (PRA B, PRA A). Until recently it was though that the causative gene for PRA B is PPT1, however the penetrance of tested mutation was only 79% leaving a large proportion of PRA B cases unexplained. In 2020 Kaukonen et al. analysed PRA affected Miniature Schnauzers and found that there are 2 types of PRA B – PRA B1 associated with HIVEP3 gene explaining majority of cases and PRA B2 associated with chromosome X (at the moment mutation not known).

In our laboratory we test HIVEP3 gene mutation which was demonstrated to be fully penetrant and concordant with clinical signs. Not all cases of PRA can be explained by this genetic test in Miniature Schnauzers as at least one distinct form of PRA is present in the breed beside HIVEP3 associated PRA B1.

Inheritance: autosomal recessive

Mutation: HIVEP3 gene

Genetic test: The method used for testing is extremely accurate and allows complete differentiation between affected animals, carriers and healthy dogs. Testing can be done at any age.