Chondrodysplasia (CDPA): A FGF4 retrogene insertion on chromosome 18 is linked to short-limbed phenotype in breeds such as Basset Hound, Pembroke Welsh Corgi, Dachshund, and Scottish Terrier.
Chondrodystrophy (CDDY) - Caused by an insertion of a fibroblast growth factor 4 (FGF4) retrogene on dog chromosome 12 (CFA12), which alters the structure and function of intervertebral discs and leads to limb shortening. Inheritance: The mutation is inherited in a semi-dominant manner for limb length—dogs with one copy have semi-shorter legs, and two copies lead to even shorter legs. However, the risk for intervertebral disc degeneration (IVDD) is autosomal dominant; one mutated allele is enough to increase disc disease risk. Breeds Affected: Chondrodystrophy and increased IVDD risk are found in many breeds, especially Dachshunds, Welsh Corgis, Pekingese, Shih Tzu, Cocker Spaniel, French Bulldog, Beagle, Basset Hound, and more.
Pathophysiology - Chondrodystrophy leads to premature degeneration and calcification of intervertebral discs, starting from a young age (birth–1 year).The abnormal discs lose flexibility and are prone to herniation into the spinal canal, causing inflammation, pain, and neurological symptoms. There is a much higher risk of acute disc herniation and rapid onset of paralysis or severe pain in affected dogs.
Complications - Spinal/Neurological: Risk of intervertebral disc herniation (IVDD), leading to back pain, paresis or paralysis, and loss of bladder/bowel control. Prognosis: IVDD may lead to permanent neurological deficits or require surgical intervention. Mortality rate is substantial and veterinary care costs can be high. Quality of Life: Dogs with severe IVDD can permanently lose mobility and require ongoing care or euthanasia if quality of life is poor.
Why This Matters to Breeders and Vets - Breeders: Genetic testing for the CFA12 FGF4 retrogene is strongly recommended for breeding programs, especially in high-risk breeds. Avoiding breeding dogs with the mutation can reduce disease incidence over time, but consider breed standards and diversity. Vets: Early recognition and genetic counseling are crucial. Clinicians must be alert for signs of IVDD in chondrodystrophic breeds and advise owners on risk, preventive care, and treatment options, including surgery and physical therapy. Population Health: The widespread presence of these mutations in many breeds means coordinated testing and breeding strategies are needed to reduce disease prevalence without excessively narrowing breed gene pools.