Photoreceptive Abiotrophy of the Retina in the Elkhound

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Abstract
An idiopathic degeneration involving predominantly the photoreceptors of the retina occurs in the elkhound similar to that which has been reported in other breeds of dogs and analogous to that which occurs in mice and men. It is suggested that the term applied to the comparable condition in man, retinitis pigmentosa, is inappropriate. A preferred name is photoreceptive abiotrophy of the retina. Photoreceptive abiotrophy in the present eight cases appeared to be a mendelian recessive trait producing signs at 6–8 months of age consisting of night blindness, narrowing of the retinal vessels and extinction of the electroretinogram. Pathologically it consists of degeneration of the photoreceptive cells and paradoxic obliteration of the retinal capillaries. Electron microscopy reveals disorganization and fragmentation of the outer segments of the rods and cones and pleating of the inner surface of the pigment epithelium, long before any abnormality is detectable by light microscopy. The pathogenesis of photoreceptive abiotrophy is obscure but in the early case here reported no abnormality was detected in diaphorase activity nor in glycogeneogenesis although there was a paucity of glycogen in the retinal glia and an absence of the normal capacity for glycogen synthesis at a later stage.

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