Oculoskeletal Dysplasia (OSD) is unusual as in addition to the condition of retinal dysplasia (retinal folds), there is also a serious inherited skeletal (bone) malformations. This leads to dwarfism (shortened limbs) and blindness at an early age - generally from the retina not forming correctly and either partial or full retinal detachment and cataracts. Please note that tests for OSD only identify the risks for this specific disease, and not all forms of retinal dyslplasia (RD). The OSD mutation does not appear to be a ?simple? recessive inheritance. Carriers typically show symptoms of RD, sometimes called ?mild? or partial expression of OSD in the Carrier. Two copies of the OSD mutation (i.e. "affected") can lead to full expression of OSD?i.e. dwarfism and blindness. It is thought that OSD has an autosomal recessive inheritance, but with incomplete penetrance. It is especially important for breeding stock for this disease to follow any breeding guidelines with test results very carefully and/or seek professional advice.
It is currently thought that the causative mutation leads to collagen absence or deficiency in cartilage and ocular collagen, with a larger effect in vitreous and retinal tissue than in the limbs (Goldstein et al., 2010). Signs may be noticeable as early as 4 to 6 weeks of age. Affected dogs also have short-limbed dwarfism and vitreous dysplasia. In pups, the dome of the cranium is often pronounced and there is moderate excessive exotropic strabismus. Some, but not all, carriers have vitreal stands, focal retinal folds or plaques of retinal dysplasia. There is a range of ocular defects, but the most consistent findings are cortical equatorial cataracts and vitreal liquefaction. Histologic lesions in the growth plates included disorganization of cellular columns with abnormal extent of calcification, great variability in chrondrocyte shape, and premature cellular condensation in the maturation zone. Associated ophthalmic lesions include retinal detachment and cataracts.There is a test available to detect the causative mutation. Affected dogs are not reliably identified by clinical signs alone, so suspected dogs should be tested. Dogs having mild ocular lesions may be carriers and should be tested.
Goldstein, O., Guyon, R., Kukekova, A., Kuznetsova, TN., Pearce-Kelling, SE., Johnson, J., Aguirre, GD., Acland, GM. : COL9A2 and COL9A3 mutations in canine autosomal recessive oculoskeletal dysplasia. Mamm Genome 21:398-408, 2010. Pubmed reference: 20686772. DOI: 10.1007/s00335-010-9276-4.
Choosing a Genetic Test Provider Choosing a genetic test provider can be daunting. This short article helps you to consider what is important to you, and your dogs, in finding the right test provider for you.
The HGTD genetic counselling resources index link above and links below provide access to basic introductory articles on genetics, articles on application of genetics in breed health management and advanced work in technical genetics research. Breed-specific information is also available in DWN's Pedigreed Dogs Database.