Retinal dysplasia in American pit bull terriers - phenotypic characterization and breeding study

Objective The purpose of this study was to investigate the inheritance and phenotype of retinal dysplasia (RD) in the American pit bull terrier. Animals Studied A breeding colony established from a single female pure-bred American pit bull terrier dog with RD. Procedures A female pure-bred American pit bull terrier with RD was donated to the Veterinary Hospital of Federal University of Parana, Curitiba, Brazil. A breeding colony was established and the phenotype and inheritance of the condition investigated. Regular ophthalmic examinations and fundus photography were performed on three generations of offspring from the founder animal. Some animals were additionally studied by optical coherence tomography. Ocular histopathology was performed on some animals from the colony. Results Fifty-seven offspring were produced in two generations from the affected founder female. Thirty-two were diagnosed with RD and showed a spectrum of severity of lesions including multifocal, and or geographic lesions and some developed retinal detachment. Histologic examination demonstrated retinal folds, rosettes, and areas of retinal detachment. The affected dogs were shorter in stature than the unaffected littermates. Breeding studies suggested the trait has an autosomal dominant mode of inheritance. DNA testing showed that the affected dogs were negative for the known gene mutations for canine dwarfism with RD. Conclusion This is a report of a novel inherited form of RD that affects American pit bull terriers.