Retinal dysplasia/oculoskeletal dysplasia 2 is an inherited Collagen disorder affecting dogs. Dwarfism and eye abnormalities may be apparent as early as 4 to 6 weeks of age in affected puppies. The dwarfism is characterized by shortened forelimbs that become curved as the dog grows. In puppies, the top of the head may be noticeably domed compared to littermates. A range of eye abnormalities are visible on a veterinary eye exam of which retinal detachment and cataracts are the most common. Carrier dogs do not have skeletal changes but may have mild eye abnormalities.
Genetic testing of the COL9A2 gene will reliably determine whether a dog is a genetic Carrier of retinal dysplasia/oculoskeletal dysplasia 2. Retinal dysplasia/oculoskeletal dysplasia 2 is inherited in an autosomal incomplete dominant manner in dogs meaning that dogs only need to inherit one copy of the mutated gene to be at an increased risk of developing the disease. In general, carrier dogs will not display skeletal abnormalities associated with this disorder, but carrier dogs may have mild eye defects (e.g. retinal folds). When bred with another carrier of the same Mutation, there is a risk of having pups with severe eye and skeletal abnormalities. Each pup that is born to this pairing has a 25% chance of inheriting two copies of the mutation and developing the severe form of the disease and a 50% chance of inheriting one copy and being at risk for retinal folds. Reliable genetic testing is important for determining breeding practices. In order to eliminate this mutation from breeding lines and to avoid the potential of producing affected pups, breeding of known carriers to each other is not recommended. Dogs that are not carriers of the mutation have no increased risk of having affected pups.
There may be other causes of this condition in dogs and a normal result does not exclude a different mutation in this gene or any other gene that may result in a similar genetic disease or trait.
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. 2010 Aug; 21(7-8):398-408.