This test evaluates two regions of the canine genome to identify a Mutation on canine Chromosome 12 associated with chondrodystrophy and intervertebral disc disease (CDDY and IVDD Risk) and a mutation on canine chromosome 18 associated with chondrodysplasia (CDPA).
Chondrodystrophy with Intervertebral Disc Disease Risk Factor (CDDY with IVDD):
Intervertebral disc disease (IVDD) is an inherited disease affecting many dog breeds. A severe form of IVDD is associated with a genetic mutation in the FGF4 gene on canine chromosome 12. This genetic mutation is also identified as one cause of the characteristic trait for short legs (chondrodystrophy) in some dog breeds. Dogs affected with IVDD have premature degeneration and calcification of the cartilage discs that connect the vertebrae and function as shock absorbers for the spine. In some cases, these degenerative changes result in cartilage weakness and subsequent herniation of the discs into the spinal cord, causing Hemorrhage and inflammation. Affected dogs present with a variety of neurological clinical signs including severe back pain, abnormal gait, loss of balance, and limb weakness or paralysis, often requiring surgical intervention. Affected dogs are at risk of experiencing disc herniations at multiple sites along their spine during their lifetime. Therefore, it is common for dogs which have been surgically treated for disc herniation to experience a herniation in another location of the spine later in life.
Leg length is one of the traits that varies significantly among dog breeds. The characteristic short-legged trait of some breeds is referred to as chondrodysplasia (CDPA) but is also known as short-limbed or disproportional dwarfism. The trait is found in many breeds including the Dachshund, Pekingese, Corgi, and Basset Hound. Chondrodysplasia is inherited in an Autosomal Dominant manner and is associated with an insertion of a duplicate copy of the FGF4 gene (known as a retrogene insertion) on chromosome 18. It is thought that this mutation causes premature activation of other growth factor receptors leading to early calcification of the long bones resulting in limbs with a short and curved appearance. Although many breeds of dog with short legs carry two copies of the mutation, some carry only one or none, suggesting that there are other genetic factors responsible for short legs in other breeds including the mutation on canine chromosome 12 associated with chondrodystrophy and intervertebral disc disease risk (CDDY with IVDD).