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Canine Mendelian disease record

Chondrodystrophy and Intervertebral Disc Disease Risk (CDDY)

Chondrodystrophy and Intervertebral Disc Disease Risk (CDDY). Autosomal dominant. Observed in 113 of 266 breeds tested in the Sniff Atlas, with measured allele frequencies drawn from 241,530 dogs (Donner 2023). Because this is a dominant trait, a single copy places a dog at risk rather than making it a silent carrier; whether the phenotype appears still depends on penetrance, modifier genes, and environment.

Dominant trait. A single copy of this variant places a dog at risk; it does not make the dog a silent carrier. The breed frequencies below are therefore at-risk frequencies, and penetrance plus modifier genes determine whether the phenotype actually appears.

OMIA identifier
OMIA:000157-9615
Autosomal dominant
Source dataset
Sniff Atlas v1.0.2 / DOI
The plain version

Chondrodystrophy and Intervertebral Disc Disease Risk (CDDY) affects the spine, involving changes to the discs between vertebrae that can impact mobility and comfort. It is related to the development and health of the spinal discs.

How it is inherited. This condition is inherited in an autosomal dominant way, meaning that having just one copy of the gene variant can increase risk.

It is found in several breeds including Cavalier King Charles Spaniel, Nova Scotia Duck Tolling Retriever, English Springer Spaniel, Havanese, and Yorkshire Terrier, with varying levels of carriers in each breed.

Being a carrier is not the same as being affected, but it’s worth asking your vet about testing if you have one of these breeds to better understand your dog's risk.

Allele frequency in well-studied breeds
  • Dachshund Miniature Longhaired · 100%
  • Cavalier King Charles Spaniel · 99%
  • Cocker Spaniel · 99%
  • Dachshund Miniature Shorthaired · 95%
  • English Cocker Spaniel · 94%
  • Cardigan Welsh Corgi · 94%

Educational carrier context from the Sniff disease layer (Donner 2023 (allele frequencies) + substrate; educational, not diagnostic). Not a diagnosis and not a prediction about your dog. See the full allele-frequency chart below for sample sizes and the Donner cohort when available.

Context source: Donner 2023 (allele frequencies) + substrate; educational, not diagnostic · dataset doi:10.5281/zenodo.20566358 . We would rather give you a short plain summary with a receipt than invent comfort.

About this disease

From OMIA's curated record

Documented in OMIA (Online Mendelian Inheritance in Animals). This describes the disease as recorded in the published literature, not a prediction for any individual dog. As of 2026-08-27.

Summary

"Two FGF4 retrogenes (FGF4L1 on chromosome 18 and FGF4L2 on chromosome 12) have been identified to cause dwarfism across many dog breeds. Some breeds are nearly homozygous for both retrogenes (e.g., Dachshunds) and others are homozygous for just one (e.g., Beagles and Scottish Terriers)" (Bannasch et al., 2022)

Clinical features

Batcher et al. (2019) concluded that "The FGF4 retrogene on CFA12 acts in a dominant manner to decrease the age of onset and increase the overall risk of disc disease in dogs. Other modifiers of risk may be present within certain breeds, including the FGF4 retrogene on CFA18." In Nova Scotia Duck Tolling Retrievers, Murphy et al. (2019) concluded that dogs with the retrogene variant present with clinical signs "consistent with premature chondroid degeneration of the intervertebral disc and suggest that the presence of the CFA12 FGF4 retrogene is sufficient to cause the chondrodystrophic phenotype."

Molecular genetics

Brown et al. (2017) reported that an FGF4 retrogene insertion in chromosome CFA12 (12: g.33710178_33710179insMF040221.1; CanFam3) is "responsible for type I IVDD . . . across dog breeds . . . the insertion on CFA12 is 3,209 bp long (GenBank accession no. MF040221) and includes parental FGF4 cDNA (i.e., FGF4 exons spliced without introns) . . . . The insert also contains a majority of the predicted 5′-untranslated region (UTR), which includes the transcription start site (TSS) as only PCR primers FGF4_TSS.F1 and FGF4.R1 yielded a product in RT-PCR using cDNA from neonatal beagle IVD . . . . The insertion location is intergenic between the 3′-UTR of OGFRL1 ∼9.5 kb on the proximal side and ∼350 kb to the RIMS1 gene on the distal side." Because the retrogene is not included in NCBI's Gene database, the table below lists the normal FGF4 gene.

Inheritance

Brown et al. (2017): "IVDD-affected NSDTRs were also all either homozygous or heterozygous for the CFA12 FGF4 insertion. This supports the idea that while the CFA12 FGF4 insertion is semidominant with respect to height, it is dominant for altered IVDs" Bannasch et al. (2022): "Using individual measurements of height at the shoulder, back length, head width, thorax depth and width, and thoracic limb measurements, we evaluated the combined effects of FGF4 retrogenes [FGF4L1 and FGF4L2] within" two breeds that segregate both retrogenes, namely Alpine Dachsbracke and the Schweizer Niederlaufhund. They found that "both retrogenes had significant effects reducing height at the shoulders and antebrachial length, with FGF4L1 having a much greater effect than FGF4L2. FGF4L1 alone influenced the degree of carpal valgus and FGF4L2 alone increased head width. Neither retrogene had an effect on thorax width or depth." From a detailed analysis of 569 surgical cases of IVDD, Batcher et al. (2019) concluded that "The FGF4 retrogene on CFA12 acts in a dominant manner to decrease the age of onset and increase the overall risk of disc disease in dogs. Other modifiers of risk may be present within certain breeds, including the FGF4 retrogene on CFA18."

History

As summarised by Brown et al. (2017): "Hansen [1951, 1952] described the two different types of canine IVD prolapse as type I and type II. Type I occurs exclusively in chondrodystrophic breeds [e.g. "basset hound, Pembroke Welsh corgi, and dachshund"] and is characterized by premature degeneration of all discs in young dogs. In contrast, type II occurs in older dogs and is usually limited to a single disc with only partial protrusion."

Control

Bruun et al. (2020) concluded that "Our results show that the FGF4 retrogene insertion on CFA12 is not a valid risk indicator on its own. Relying on the DNA test will have an irreversible effect on the Dachshund breed excluding almost all dogs from breeding. Thus, using calcification status remains the most reliable breeding scheme for disc herniation in Dachshunds." Bannash et al. (2022) recommend that "Selectively breeding dogs with FGF4L1 and without FGF4L2 would likely lead to a reduction in the FGF4L2-related risk of intervertebral disc herniation while maintaining the reduction in leg length resulting from FGF4L1."

Source: OMIA (Nicholas, Tammen & the Sydney Informatics Hub), entry OMIA:000157-9615, doi:10.25910/2AMR-PV70 (CC-BY 4.0).

OMIA curates the disease definition, the clinical description and the reference list. The cross-species disease identity is Monarch's. Sniff renders these and adds the breed-level frequencies, the plain-language summary, and a stated reason wherever a number is missing.

The evidence

Published references

The peer-reviewed papers behind this disease, curated by OMIA. Starred entries are OMIA-designated landmark papers. Showing 6 of 84.

  2. Dachshund spinal health by coat and size type. · J Vet Intern Med · 2026 · PMID 42531050

References curated by OMIA (Nicholas, Tammen & the Sydney Informatics Hub), doi:10.25910/2AMR-PV70 (CC-BY 4.0). Full list at the OMIA entry.

In plain terms

Chondrodystrophy and disc disease risk (CDDY)

  • Two extra copies of a growth gene, FGF4, shape dog legs and spines. The one on chromosome 12 is the one tied to disc disease; the one on chromosome 18 shortens legs.
    OMIA 000157-9615

    “Two FGF4 retrogenes (FGF4L1 on chromosome 18 and FGF4L2 on chromosome 12) have been identified to cause dwarfism across many dog breeds.” OMIA 000157-9615

    “Brown et al. (2017) reported that an FGF4 retrogene insertion in chromosome CFA12” OMIA 000157-9615

  • Carrying it raises risk. It does not say which dog will have a disc problem. In Dachshunds researchers found the test is not a valid risk indicator on its own.
    OMIA 000157-9615

    “the FGF4 retrogene insertion on CFA12 is not a valid risk indicator on its own” OMIA 000157-9615

What to do
Ask your veterinarian what a carrier result changes for your dog. What lowers risk in a carrier is not established in the sources this page draws on.

No test, or a mix
Without a test nobody can say whether a dog carries it. Leg length alone does not tell you: the disc-disease copy and the short-leg copy are different insertions.

Predict a litter

Set each parent's status for Chondrodystrophy and Intervertebral Disc Disease Risk (CDDY) and see the odds for their puppies. Single dominant variant, exact Mendelian math.

Parent A
Parent B
NDAffected
NDAffected
NNUnaffected
NNUnaffected
Unaffected50%
Affected50%

These are the genetic odds for one known variant, not a promise: a real litter varies around them, and penetrance or other genes can change whether the condition ever appears. One copy is enough, so a parent with the variant passes it to about half the litter whatever the mate. Use it to keep a line healthy, not to engineer a dog. Inheritance mode per OMIA.
Your breed

See what Chondrodystrophy and Intervertebral Disc Disease Risk (CDDY) looks like in your dog's breed.
Allele frequency by breed

Top 25 well-sampled breeds (n ≥ 50)

Maximum per breed across variants in the Donner 2023 cohort, with . The list below is split into well-sampled breeds (n ≥ 50 tested) and small-sample breeds (n < 50, where the Wilson CI typically spans more than 20 percentage points and frequencies should not be compared directly to the well-sampled entries). Frequencies are population-level, not per-litter or per-line.

0%50%100%
Dachshund Miniature Longhaired99.5% · n 213
Cavalier King Charles Spaniel99.0% · n 2,232
Cocker Spaniel98.5% · n 1,870
Dachshund Miniature Shorthaired95.1% · n 583
English Cocker Spaniel94.0% · n 579
Cardigan Welsh Corgi93.5% · n 124
Beagle93.5% · n 5,245
French Bulldog87.9% · n 13,062
Poodle Toy81.9% · n 94
Pembroke Welsh Corgi80.4% · n 4,351
Spanish Water Dog71.5% · n 93
Papillon68.3% · n 197
Basset Hound67.5% · n 982
Poodle Miniature63.4% · n 3,544
Boykin Spaniel59.1% · n 154
n = 33,323 dogs · Donner et al. 2023 carrier-screening cohort · Sniff Atlas
n counts the dogs in the breeds charted here; the page total above counts every breed screened. Each bar is one well-sampled breed; the whisker is its Wilson 95% CI, and fainter bars have wider intervals. Frequencies are population-level, not per-litter. Carrier status for Chondrodystrophy and Intervertebral Disc Disease Risk (CDDY) is measured; phenotype outcome depends on penetrance and modifiers.
▸ Full table with Wilson 95% confidence intervals
Breed Allele frequency n tested
Dachshund Miniature Longhaired 99.5% 213
Cavalier King Charles Spaniel 99.0% 2,232
Cocker Spaniel 98.5% 1,870
Dachshund Miniature Shorthaired 95.1% 583
English Cocker Spaniel 94.0% 579
Cardigan Welsh Corgi 93.5% 124
Beagle 93.5% 5,245
French Bulldog 87.9% 13,062
Poodle Toy 81.9% 94
Pembroke Welsh Corgi 80.4% 4,351
Spanish Water Dog 71.5% 93
Papillon 68.3% 197
Basset Hound 67.5% 982
Poodle Miniature 63.4% 3,544
Boykin Spaniel 59.1% 154
Kooikerhondje 56.1% 197
Pekingese 41.6% 238
Chinese Crested 31.8% 201
Nova Scotia Duck Tolling Retriever 29.4% 63
Coton De Tulear 28.4% 104
Chinook 24.4% 80
English Springer Spaniel 23.6% 749
Danish Swedish Farmdog 20.8% 60
Bichon Frise 20.8% 1,059
Biewer Terrier 20.1% 184

Top 25 of 80 well-sampled breeds with at least one observed carrier shown.

▸ Also observed in 33 small-sample breeds (n < 50)

Frequencies in this section are statistical estimates with wide Wilson 95% confidence intervals (typically >20 percentage points). Treat these as "at-risk dogs observed but the true population frequency is not yet measurable" rather than as comparable to the well-sampled entries above.

Breed Estimate n tested
Bavarian Mountain Hound 100.0% 8
Clumber Spaniel 100.0% 12
Continental Toy Spaniel 100.0% 8
Dachshund Longhaired 100.0% 1
Dachshund Shorthaired 100.0% 6
Dachshund Wirehaired 100.0% 4
Dandie Dinmont Terrier 100.0% 1
English Toy Spaniel 100.0% 2
Field Spaniel 100.0% 28
Poodle Medium 100.0% 1
Skye Terrier 100.0% 4
Sussex Spaniel 100.0% 3
Welsh Springer Spaniel 91.7% 12
American Water Spaniel 83.3% 6
Polish Lowland Sheepdog 83.3% 3
Entlebucher Mountain Dog 77.3% 11
Sealyham Terrier 75.0% 4
Stabyhoun 66.7% 27
Alpine Dachsbracke 50.0% 1
Schapendoes 47.8% 45
Drever 25.0% 4
Lowchen 25.0% 4
Puli 25.0% 12
Bedlington Terrier 22.7% 11
German Spitz 16.7% 3
Pyrenean Shepherd 15.5% 29
Tibetan Spaniel 11.5% 39
Bolognese 10.0% 5
Russian Toy 10.0% 5
Russian Tsvetnaya Bolonka 10.0% 15
Munsterlander Small 6.7% 15
German Hunting Terrier 3.8% 13
Silky Terrier 1.8% 28

153 additional breeds in the Donner 2023 cohort were tested but showed no at-risk genotypes.

Scope of this record

Scope

This record carries the breed-level allele frequencies from the Donner 2023 cohort. Penetrance data (the fraction of at-risk dogs that develop the phenotype) is not yet quantified for this disease in the Sniff Atlas v1.0.2. The OMIA entry is the authoritative reference for the clinical phenotype, inheritance pattern, and gene assignment.

Predicted disease relevance at the per-dog level is UNPROVEN. The allele frequency is measured; phenotype outcome depends on penetrance, environment, and modifier loci. Consult a veterinarian for clinical interpretation.

How to cite this record

Citations

If you use this record in published work, cite the Sniff Atlas (the published dataset that carries the breed-level allele frequencies) and the upstream sources:

  • Sniff Atlas v1.0.2 for the per-breed allele frequencies:

    Gehring, M. (2026). Sniff Atlas v1.0.2. Zenodo. https://doi.org/10.5281/zenodo.20566358. CC-BY 4.0.

  • OMIA for the disease definition, inheritance, and gene assignment:

    Nicholas, F. W., & Tammen, I. (2024). OMIA. Sydney Informatics Hub, The University of Sydney. https://doi.org/10.25910/2AMR-PV70. Entry: OMIA:000157-9615.

  • Donner et al. 2023 for the breed × variant allele-frequency cohort:

    Donner, J., Freyer, J., Davison, S., Anderson, H., Blades, M., Honkanen, L., et al. (2023). Genetic prevalence and clinical relevance of canine Mendelian disease variants in over one million dogs. PLOS Genetics, 19(2), e1010651. https://doi.org/10.1371/journal.pgen.1010651.

Full citation formats (BibTeX, RIS, CITATION.cff) at sniff.world/cite.

Related

Related

Last updated
Sources: Sniff Atlas v1.0.2 · OMIA OMIA:000157-9615 · Donner et al. 2023