Generalized progressive retinal atrophy in two Akita dogs.

Two distantly related, two- to three-year-old male Akita dogs developed partial or complete night blindness which progressed to day blindness. Clinical features were attenuated retinal blood vessels, diffuse exaggerated tapetal reflex, and hyperreflective horizontal lines in the tapetal fundus. The principal histologic change was regional photoreceptor cell degeneration. Areas of moderately atrophic sensory retina alternated, concentrically to the papilla, with areas of severely atrophic retina. Ultrastructurally, there was disorganization of photoreceptor outer segments, retinal gliosis, focal loss with reorganization of the outer limiting membrane, and retinal invasion by pigment epithelium-derived macrophages. Clinical observations on five additional Akitas with generalized retinal atrophy suggest that the condition is heritable.