CDDY IN FRENCH BULLDOGS

Genetics • Spine Health • IVDD • Breeding

WHAT IS CDDY?

CDDY = Chondrodystrophy.

CDDY is associated with an FGF4 retrogene on canine chromosome 12, commonly called 12-FGF4RG or FGF4-12.

In French Bulldogs, this genetic variant is important because it is associated with:

  • Shorter limbs

  • Premature intervertebral-disc degeneration

  • Disc calcification

  • Increased susceptibility to Hansen Type I IVDD

The important point

CDDY is a genetic risk factor — not an IVDD diagnosis.

WHY DOES CDDY MATTER?

French Bulldogs are naturally a chondrodystrophic breed, and CDDY is extremely common within the breed.

The CDDY-associated FGF4 variant affects the biology of the intervertebral discs.

A simplified pathway is:

FGF4-12

↓

Altered FGF4 signaling

↓

Premature disc degeneration

↓

Disc calcification

↓

Greater susceptibility to disc herniation

↓

Possible IVDD

CDDY & THE INTERVERTEBRAL DISC

Each spinal disc contains two primary components:

Annulus Fibrosus

The strong outer ring.

Nucleus Pulposus

The softer inner portion.

In CDDY-associated chondrodystrophy, the disc can undergo premature degeneration and calcification.

As the disc degenerates, it can become more susceptible to herniation.

CDDY DOES NOT EQUAL IVDD

This distinction is extremely important.

CDDY

A genetic variant associated with increased risk.

IVDD

A clinical disease involving degeneration and/or herniation of intervertebral discs.

Therefore:

CDDY-positive ≠ guaranteed IVDD

And:

CDDY-negative ≠ guaranteed IVDD-free

IVDD is a complex, multifactorial condition.

CDDY GENOTYPES

N/N

0 copies

No CDDY-associated variant detected.

Generally means the dog does not carry the CFA12 CDDY variant.

However, the dog can still develop IVDD from other genetic, structural, or environmental factors.

N/CDDY

1 copy

The dog carries one CDDY copy.

One copy is already associated with increased susceptibility to premature disc degeneration and IVDD.

This dog can pass CDDY to approximately 50% of its offspring when bred to an N/N dog.

CDDY/CDDY

2 copies

The dog carries two CDDY copies.

Two copies are associated with the CDDY phenotype and increased susceptibility to premature disc degeneration.

When bred to an N/N dog:

100% of puppies are expected to inherit one CDDY copy.

CDDY & IVDD RISK

Think of CDDY as a risk factor, not a prediction.

CDDY can increase:

  • Premature disc degeneration

  • Disc calcification

  • Susceptibility to disc herniation

  • Risk of Hansen Type I IVDD

  • Potential for earlier clinical disease

But CDDY does NOT tell you:

  • Whether a dog currently has IVDD

  • Whether a disc is currently herniated

  • How many discs are calcified

  • When IVDD will occur

  • Whether surgery will ever be necessary

CAN N/N DOGS GET IVDD?

YES.

This is one of the most important facts for breeders.

An N/N result lowers CDDY-associated risk, but it does not eliminate all possible causes of IVDD.

Other factors may include:

  • Other genes

  • Spinal anatomy

  • Disc structure

  • Vertebral abnormalities

  • Body condition

  • Trauma

  • High-impact activity

  • Age

  • Environmental factors

Bottom line:

N/N = lower CDDY-associated risk

NOT = zero IVDD risk

CDDY VS CDPA

These two genetic variants are often confused.

CDPA

Chondrodysplasia

Primarily associated with limb shortening.

CDDY

Chondrodystrophy

Associated with limb shortening and premature intervertebral-disc degeneration/IVDD susceptibility.

A French Bulldog can potentially carry both variants.

CDDY VS HEMIVERTEBRAE

They are not the same condition.

CDDY

A genetic variant involving the FGF4 retrogene on CFA12.

Hemivertebrae

A congenital vertebral malformation caused by abnormal development of a vertebra.

A French Bulldog can have:

CDDY without significant hemivertebrae

Hemivertebrae without CDDY

or

Both.

A CDDY DNA test does not diagnose hemivertebrae.

CDDY VS ROACH BACK

A roach-backed French Bulldog should not automatically be assumed to have CDDY-related spinal disease.

Topline appearance can be influenced by:

  • Vertebral structure

  • Body proportions

  • Musculature

  • Conformation

  • Genetics

  • Individual anatomy

Likewise:

A beautiful topline does not prove that the discs are healthy.

Appearance and genetic testing answer different questions.

WHAT DOES AN EMBARK CDDY RESULT TELL YOU?

A CDDY DNA result tells you whether the dog carries the CFA12 FGF4-associated variant.

It does not tell you whether the dog currently has:

  • A herniated disc

  • Disc compression

  • Neurological disease

  • Hemivertebrae

  • Disc calcification

  • Spinal cord compression

DNA testing = genetic information

Imaging = physical/anatomical information

They complement each other.

HOW IS SPINAL HEALTH EVALUATED?

Depending on the clinical question, veterinarians may use:

Physical & Neurological Examination

Evaluates:

  • Gait

  • Strength

  • Reflexes

  • Pain

  • Coordination

  • Neurological function

Radiographs

Can help evaluate:

  • Vertebral anatomy

  • Some spinal abnormalities

  • Visible disc calcification

CT

Provides detailed information about bony spinal structures.

MRI

Provides detailed information about:

  • Intervertebral discs

  • Spinal cord

  • Disc herniation

  • Compression

  • Soft tissues

CDDY & DISC CALCIFICATION

Disc calcification is an important part of the CDDY story.

Research has found an association between additional CDDY copies and increased numbers of radiographically visible calcified discs.

This helps explain why CDDY is associated with premature disc degeneration.

However:

Disc calcification does not automatically mean the dog will suffer a clinical disc herniation.

HOW EARLY CAN CHANGES BEGIN?

The CDDY-associated disc phenotype can develop very early in life.

Research has reported evidence of the phenotype in young dogs.

This does not mean a puppy will necessarily develop clinical IVDD.

It means that the underlying biological process can begin long before obvious neurological symptoms appear.

CDDY & BREEDING

For breeders, CDDY should be considered as one part of a larger breeding-health strategy.

Evaluate:

GENETICS

  • CDDY

  • CDPA

  • Other relevant health tests

  • COI

  • Genetic diversity

STRUCTURE

  • Topline

  • Movement

  • Limb structure

  • Vertebral anatomy

  • Overall balance

SPINAL HEALTH

  • Veterinary examination

  • Relevant imaging

  • Disc history

  • Neurological history

FAMILY HISTORY

Look at:

  • Parents

  • Grandparents

  • Siblings

  • Half-siblings

  • Previous offspring

  • Older relatives

Ask:

Has IVDD occurred repeatedly within this family?

CDDY & COI

These are completely different measurements.

CDDY

A specific genetic variant.

COI

A measure of genetic relatedness/inbreeding.

A dog can be:

Low COI + CDDY positive

or

High COI + CDDY negative

They answer different questions.

BREEDING PAIRINGS

N/N × N/N

Expected:

100% N/N

N/N × N/CDDY

Expected:

50% N/N

50% N/CDDY

N/N × CDDY/CDDY

Expected:

100% N/CDDY

N/CDDY × N/CDDY

Expected:

25% N/N

50% N/CDDY

25% CDDY/CDDY

N/CDDY × CDDY/CDDY

Expected:

50% N/CDDY

50% CDDY/CDDY

CDDY/CDDY × CDDY/CDDY

Expected:

100% CDDY/CDDY

SHOULD CDDY-POSITIVE DOGS BE REMOVED?

There is no simple "positive = never breed" rule that captures the entire problem.

CDDY is extremely common in French Bulldogs.

Removing large numbers of dogs from breeding solely because they carry CDDY could potentially reduce genetic diversity and increase other genetic risks.

A better approach is:

REDUCE RISK

while also

PRESERVING GENETIC DIVERSITY

and selecting for:

  • Healthy structure

  • Good movement

  • Appropriate body condition

  • Strong overall health

  • Favorable family history

  • Responsible genetic pairings

WHAT CDDY CANNOT TELL YOU

A CDDY test cannot predict:

❌ Exact age of IVDD onset
❌ Whether IVDD will occur
❌ Whether surgery will be needed
❌ Number of affected discs
❌ Presence of hemivertebrae
❌ Current disc herniation
❌ Current spinal-cord compression
❌ Overall spinal health

It provides important genetic-risk information, but it is not a complete spinal-health examination.

THE BIG PICTURE

Think of French Bulldog spinal health as several pieces of a puzzle:

1. CDDY

Genetic predisposition to premature disc degeneration.

2. VERTEBRAL ANATOMY

Hemivertebrae and other structural abnormalities.

3. DISC HEALTH

Degeneration and calcification.

4. OTHER GENETICS

Additional genes may influence IVDD susceptibility.

5. ENVIRONMENT

Activity, trauma, body condition and other factors.

6. INDIVIDUAL DOG

Every dog can respond differently.

CDDY IN ONE SIMPLE DIAGRAM

CDDY

↓

FGF4-12 RETROGENE

↓

ALTERED FGF4 SIGNALING

↓

PREMATURE DISC CHANGES

↓

DISC DEGENERATION / CALCIFICATION

↓

INCREASED SUSCEPTIBILITY

↓

POSSIBLE DISC HERNIATION

↓

POSSIBLE IVDD

BUT:

RISK ≠ CERTAINTY

RESPONSIBLE BREEDING PRINCIPLE

The goal should not simply be:

"Eliminate one gene."

The broader goal should be:

REDUCE IVDD RISK WHILE MAINTAINING GENETIC DIVERSITY AND OVERALL HEALTH.

That means considering the entire dog, pedigree, genetic profile, structure, spinal history and breeding combination.

QUICK CDDY REFERENCE

ResultCopiesMeaningN/N0No CDDY variant detectedN/CDDY1Carries CDDY; increased IVDD susceptibilityCDDY/CDDY2Two copies; increased CDDY-associated disc riskCDDY = IVDD?—NoN/N = IVDD-free?—NoCDDY = hemivertebrae?—NoCDDY = CDPA?—NoDNA test = spinal diagnosis?—No

FINAL TAKEAWAY

CDDY is one of the most important genetic factors to understand when discussing IVDD in French Bulldogs.

It is strongly associated with premature intervertebral-disc degeneration and increased susceptibility to Hansen Type I IVDD, but it does not determine an individual dog's fate.

The most responsible evaluation combines:

CDDY testing

other genetic testing

COI/genetic diversity

family IVDD history

vertebral/spinal evaluation

overall structure and health

The goal is not simply to produce a CDDY-negative dog.

The goal is to produce a healthier French Bulldog with the best possible balance of genetics, structure, spinal health, temperament and genetic diversity.