Skeletal dysplasia 2 is an inherited Musculoskeletal disease affecting Labrador Retrievers. Affected dogs develop a mild form of “disproportionate dwarfism” consisting of short legs with normal body length and width. The leg bones are shorter, thicker, and slightly curved and the front legs are frequently more affected than rear legs. Joints and eyes are not typically affected with this disease. The height of affected dogs is variable, making diagnosis based on physical characteristics alone challenging in some individuals. Mildly affected dogs from bloodlines known to produce large dogs may still fall within their breed standard for height. The causal Mutation shows Incomplete Penetrance meaning that not all dogs inheriting two copies (one from each parent) will display obvious physical characteristics of dwarfism.
Genetic testing of the COL11A2 gene in Labrador Retrievers will reliably determine whether a dog is a genetic Carrier of skeletal dysplasia 2. Skeletal dysplasia 2 is inherited in an Autosomal Recessive manner in dogs meaning that they must receive two copies of the mutated gene (one from each parent) to develop the disease. In general, carrier dogs do not have features of the disease but when bred with another carrier of the same Mutation, there is a risk of having affected pups. Each pup that is born to this pairing has a 25% chance of inheriting the disease and a 50% chance of inheriting one copy and being a carrier of the COL11A2 gene mutation. Reliable genetic testing is important for determining breeding practices. Because this mutation shows Incomplete Penetrance, genetic testing should be performed before breeding. 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. Labrador Retrievers 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.
Frischknecht M, Niehof-Oellers H, Jagannathan V, Owczarek-Lipska M, Drogemuller C, Dietschi E, Dolf G, Tellhelm B, Lang J, Tiira K, Lohi H, Leeb T. A COL11A2 mutation in Labrador Retrievers with mild disproportionate dwarfism. PLoS One. 2013;8(3):e60149