Progressive retinal atrophy in cats

Sammanfattning: Progressive Retinal Atrophy (PRA) is an umbrella term used to describe a variety of inherited retinopathies observed in multiple species. This literature study focuses on PRA observed in five different cat breeds: Abyssinian, Siamese, Persian, Bengal and African black-footed cat. Various reports have described the mode of inheritance, age of onset, clinical and histological findings and specific genetic mutations seen in these breeds. The similarities and differences of these characteristics among these breeds are discussed. At least four different types of PRA have been identified in these cats: rdAc (late-onset, recessively inherited rod-cone degeneration caused by a mutation in the CEP290 gene), rdy (early-onset, dominantly inherited rod-cone dystrophy, caused by a mutation in the CRX gene), an early-onset recessively inherited rod-cone degeneration caused by one of two different genetic mutations (either an AIPL1 gene mutation or an IQCB1 gene mutation) and an early-onset recessively inherited rod-cone degeneration with unknown genetic mutation. The Abyssinian is afflicted with both rdAc and rdy. The Siamese is afflicted with one of the same mutations as the Abyssinian, rdAc. The Persian and the African black-footed cat seem to share a clinically identical early-onset recessively inherited rod-cone degeneration; however, they are caused by different genetic mutations. The Persian cat has a mutation in the AIPL1 gene and the African black-footed cat has a mutation in the IQCB1 gene. The early-onset recessively inherited rod-cone degeneration of the Bengal appears to be distinct from rdAc, rdy and the Persian (AIPL1 gene mutation). It is still unknown if the Bengal has the same mutation as the African black-footed cat. The clinical signs and histopathology of PRA among these breeds are very similar. Hyperreflectivity and retinal vessel attenuation are seen clinically in all affected cats, whilst thinning of the outer nuclear layer and outer plexiform layer and degeneration of the photoreceptor layer are usually seen histologically in those affected. These genetic mutations appear to be the same mutations observed in Leber’s congenital amaurosis (LCA) in humans. This opens up the possibility of using PRA affected cats as animal models of LCA in humans. Accurately diagnosing PRA in these breeds is important to prevent the disease via selective breeding and to enhance the quality of life for those afflicted.