Assessment of retinal function and characterization of lysosomal storage body accumulation in the retinas and brains of Tibetan Terriers with ceroid-lipofuscinosis

Abstract

Objective—To characterize lysosomal storage body accumulation in the retina and brain of Tibetan Terriers with ceroid-lipofuscinosis and determine whether the disease in these dogs is accompanied by impaired retinal function and retinal degeneration. Animals—Three 7- to 10-year-old Tibetan Terriers with ceroid-lipofuscinosis and 1 healthy 5-year-old Tibetan Terrier. Procedure—Owners completed a questionnaire to identify behavioral and physical signs indicative of ceroid-lipofuscinosis. Neurologic, behavioral, and ophthalmologic evaluations, including full-field electroretinograms, were performed on each dog. Fluorescence, light, and electron microscopy were performed on specimens of retina, cerebral cortex, and cerebellum of all dogs postmortem. Results—Behavioral assessments of the affected dogs revealed moderate visual impairment in lowlight conditions but good vision in bright light. On funduscopic evaluation of these dogs, abnormalities detected ranged from none to signs of moderately advanced retinal degeneration. Compared with findings in the control dog, electroretinography revealed depressed rod cell function with some impairment of cone cell function in the affected dogs. Morphologically, disease-specific storage bodies were detected in retinal Müller cells and neurons, particularly in ganglion cells, and in cells of the cerebral cortex and cerebellum in affected dogs. Substantial photoreceptor cell loss and disruption of photoreceptor outer segment morphology appeared to develop late in the disease. Conclusions and Clinical Relevance—The similarities between ceroid-lipofuscinosis in Tibetan Terriers and some forms of ceroid-lipofuscinosis in humans suggest that the canine disease may have a genetic and biochemical basis similar to that of one of the ceroidlipofuscinosis disorders in humans. (Am J Vet Res 2005;66:67–76)