Abstract
The light and electron microscopical characteristics of non-age-related neuronal ceroid-lipofuscinosis in a young cynomolgus monkey (Macaca fascicularis) are described. The pigment in the neuronal cytoplasm was PAS-positive, sudanophilic, weakly acid-fast, and positive with Schmorl's and aldehydefuchsin stains for lipofuscin. Ultra-structurally, it appeared as membrane-bound, electron-dense aggregates within the cytoplasm of neurones of both brain and spinal cord.