Inherited Retinal Dysplasia in Miniature Schnauzer Dogs

INHERITED RETINAL DYSPLASIA IN MINIATURE SCHNAUZER DOGS (Bruce H.Grahn, 1*, Eric S. Storey,1 and Catherine McMillan ,2). Department of Small Animal Clinical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, 52 Campus Drive, Saskatoon ,Saskatchewan, S7N 5B4; 1, Box 579, Delisle, Saskatchewan, S0L 0P0; 2, *bruce.grahn@usask.ca

Purpose. To define the clinical syndrome and determine the etiology of retinal dysplasia and persistent primary vitreous in miniature Schnauzer dogs.
Methods. We examined 106 miniature Schnauzers with a biomicroscope and an indirect opthalmoscope. Several enucleated eyes were fixed, sectioned and stained routinely. They were examined with routine light microscopy, and transmitting and scanning electron microscopy. A pedigree was constructed and related dogs were test-bred to define the mode of inheritance of this syndrome.
Results. Congenital retinal dysplasia was confirmed in 24 of 106 related miniature Schnauzer dogs. Physical and post-mortem examinations revealed that congenital abnormalities were limited to the eyes. Biomicroscopic and indirect opthalmoscopic and neuro-opthalmic examinations confirmed that many of these dogs were blind secondary to bilateral retinal dysplasia and detachment (non-attachment) n=13), and the remainder had focal areas of retinal dysplasia (n=11). Several of these dogs were also diagnosed with unilateral (n=9) or bilateral (n=6) persistent hyperplastic primary vitreous. These examinations and the pedigree and test bred litters revealed that this condition is inherited.
Conclusions. This study confirms that retinal dysplasia and persistent hyperplastic primary vitreous is a congenital syndrome that is inherited as an autosomal recessive condition in miniature Schnauzers. Supported by Companion Animal Health Research Grant 702615. None.