Understanding Chondrodystrophy (CDDY) in French Bulldogs: A Guide for Prospective Owners
- Jul 27
- 3 min read
Updated: Aug 25
What is Chondrodystrophy (CDDY)?
Chondrodystrophy (CDDY) is a genetic mutation affecting the FGF4 retrogene, found on chromosomes 18 and 12. This mutation leads to a short-legged phenotype (cfa18) and can cause premature disc degeneration, increasing the risk of disc herniation (cfa12). It serves as a risk marker for genetic testing.
The CDDY/IVDD mutation is linked to the characteristic short legs of French Bulldogs and some other breeds. Even a single copy of this variant raises the risk of disc calcification and herniated discs. Several factors influence whether a specific disc will herniate in a dog. These calcifications are categorized into three types:
Type 1 - Heritable
Type 2 - Age-related
Type 3 - Injury-related
The Genetics Behind CDDY
The short-legged phenotype seen in French Bulldogs, as well as in breeds like Dachshunds, Corgis, Shih Tzus, and Pekingese, is known as chondrodystrophy and is genetic. Let’s break down the genetics a bit more. There are two known mutations that can lead to short legs in dogs: CDDY and CDPA.
In CDDY, the mutation occurs in the FGF4 gene (Functional Fibroblast Growth Factor 4), which is crucial for bone development. This mutation is located on chromosome 12, referred to as the CFA12 FGF4 retrogene. In contrast, the CDPA mutation is found on chromosome 18, known as the CFA18 FGF4 retrogene. CDDY is classified as a risk factor for developing a disease called IVDD Type 1 (Intervertebral Disc Disease Type 1), while CDPA merely results in short legs. French Bulldogs typically carry the CFA12 mutation, while Dachshunds can have both.
How Does CDDY Cause IVDD?
So, how does CDDY lead to IVDD? The CFA12 FGF4 mutation causes premature calcification of the nucleus pulposus. This is the soft, gel-like center of the intervertebral disc located between the vertebrae. Normally, as dogs age, this nucleus is gradually replaced by fibrocartilage. However, in French Bulldogs and other breeds with CDDY, this process begins at a young age and accelerates.
When the nucleus pulposus becomes mineralized, it loses its ability to absorb shock between the vertebrae. This can lead to the disc material extruding into the spinal canal, causing bruising or compression of the spinal cord. Additional compression may occur due to hemorrhage in the canal from the ruptured disc material. Symptoms can vary based on the location and severity of the spinal cord compression, including pain, ataxia, or even paralysis of limbs.
Surgical intervention, known as a hemilaminectomy, may be necessary to alleviate compression. This procedure can cost around $10,000, and there are no guarantees of success. A study by Batcher et al. (2019) found that the average age for IVDD surgery in French Bulldogs is just 4.1 years. Other studies confirm this early onset and suggest that the DVL2 gene may also play a role. Moreover, dogs with IVDD are likely to experience another episode at a different location within the following year. The gene operates in an autosomal dominant manner, meaning that having either a double copy (homozygous) or a single copy (heterozygous) increases the risk of developing IVDD Type 1.
The Future of French Bulldogs
Interestingly, removing the DVL2 gene could alter the phenotype of the spine, making it longer and straighter. Similarly, eliminating CDDY could result in French Bulldogs with longer legs. However, since leg length is influenced by multiple genetic factors, and only a few dogs currently exist with one or no copies of this gene, it remains uncertain how they will ultimately appear.
Information originally posted by Veterinarian Dr. Adrianna from Little Frenchies on the Prairie here.
There’s also a fantastic video on YouTube presented by Embark that explains CDDY and IVDD very well.
Resources for Further Reading
By understanding the genetics and health risks associated with CDDY, we can make informed decisions when considering adding a French Bulldog to our family. Remember, choosing a breeder who prioritizes health testing and ethical breeding practices is crucial for ensuring a happy and healthy puppy! 🐾
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