Early progressive blindness from birth in Persian cats

Abstract

PURPOSE: An early-onset retinal degenerative disease has been identified in Persian cats. This study genetically, clinically, and histologically characterized the disease. A breeding colony was established to assist with identification of the causative gene and to provide a resource for vision research. METHODS: Cats were produced from testcross breedings. Kittens underwent serial ophthalmic and neuro-ophthalmic examinations. Globes were harvested from age-matched affected, obligate carrier, and control cats and were evaluated by light microscopy. Fluorescein angiography assessed retinal and choroidal vasculature. RESULTS: Test breedings confirmed an autosomal recessive mode of inheritance. Rate and extent of disease progression were similar among individual affected cats. The earliest clinical signs (reduced pupillary light reflexes) were seen at 2 to 3 weeks of age. Retinal degeneration was virtually complete by 16 weeks of age. Histologic changes progressed rapidly and paralleled clinical findings. Histologic lesions were limited to the photoreceptors, outer plexiform layer, and retinal pigment epithelium in all but the terminal stages, when subtle changes were noted within the inner nuclear layer. CONCLUSIONS: Characterized in this study was an autosomal recessive, early-onset, retinal degenerative disease in Persian cats that is likely to be more prevalent in this breed than previously suspected. This feline disease model may identify a new gene or provide biological insight into some forms of early-onset retinitis pigmentosa (RP) in humans and genetic retinal degenerations in other species. A breeding colony that will assist in the identification of the causative gene has been established and is available for studies in vision research.