The answer depends on the specific variant. DBE-CEL has not been associated with deafness in heterozygous cats studied to date. DBE-RE has been associated with sensorineural hearing loss, although not all heterozygous carriers are affected. Each variant should be evaluated individually based on current scientific evidence.

Not exactly. Waardenburg syndrome is a human condition caused by PAX3 variants and characterised by pigmentary abnormalities and sensorineural hearing loss. The DBE-RE variant in cats produces a phenotype that partially resembles Waardenburg syndrome. However, not all DBE variants produce this resemblance, and feline DBE and human Waardenburg syndrome are not identical conditions.

Ojos Azules was a breed developed in the US from cats discovered in 1984. The Ojos Azules gene was associated with lethal cranial deformities in homozygotes. The breed is now considered extinct. Modern DBE lineages are genetically distinct from Ojos Azules and involve PAX3 variants that were not identified in the original Ojos Azules population.

Not necessarily. Hearing outcomes differ between variants. Some variants have not been associated with deafness in heterozygous cats, while others have. The only reliable way to assess hearing is a BAER test — visual behaviour and response to sound cannot exclude unilateral deafness.

Yes. Many genetically confirmed DBE cats have normal bilateral hearing. However, hearing status varies between variants and between individual cats carrying the same variant. BAER testing is the only objective method of confirming hearing in both ears.

Yes. This is described as latent or non-expressing. Genetically positive cats that do not display blue eyes still have the variant and can pass it to their offspring.

A latent cat is a genetically confirmed DBE-positive cat that does not display the blue-eye phenotype. Latent cats still have the variant and can transmit it to their offspring. Latent, non-expressing cats have been documented for DBE-CEL, DBE-ALT and DBE-RE

The only reliable confirmation is a variant-specific DNA test performed on the individual kitten. Eye colour, white markings, parental status, pedigree and photographs cannot confirm which variant a kitten carries — or whether it carries one at all.

No. Blue eyes in cats can result from PAX3-associated DBE, KIT dominant white, KIT white spotting, colourpoint or other genetic causes. Appearance cannot distinguish between them.

A kitten advertised as DBE should have its own individual variant-specific genetic test confirming which DBE variant it carries, and a BAER hearing test with results recorded for each ear separately. Parental results alone are not sufficient.

BAER (Brainstem Auditory Evoked Response) is an objective test that measures auditory function in each ear independently. It is the only method that can detect unilateral deafness. Any kitten from a DBE breeding should ideally be BAER tested.

DBE is caused by variants in the PAX3 gene. White spotting is associated with the KIT gene. Both affect melanocytes but through different mechanisms — PAX3 influences their development, KIT influences their survival. Both can produce blue eyes and white markings, which is why they cannot be distinguished by appearance.

Yes. A white, bicolour, harlequin or van cat with blue eyes may carry a PAX3-associated DBE variant, KIT dominant white, KIT white spotting, both, or another unresolved cause. White coat colour does not exclude DBE.

At least six. Four are currently characterised: DBE-CEL, DBE-ALT, DBE-RE and DBE-AGO. The molecular cause of several additional DBE lineages remains unresolved.

Both are non-coding intronic variants located in intron 4 of PAX3, but they originated from different endogenous retroviral insertion events — FERV1 for DBE-CEL and RD-114 for DBE-ALT. They are distinct variants, not subtypes of each other, and should be evaluated separately.

A compound heterozygote carries two different PAX3-associated DBE variants, one inherited from each parent. This is distinct from homozygosity, where both copies are the same variant. Compound heterozygous DBE-CEL/DBE-ALT kittens with deafness have been documented in the scientific literature.

Combining PAX3-associated DBE with KIT dominant white is not recommended. Both mechanisms affect melanocytes, and melanocytes are required for normal inner-ear function. No peer-reviewed study has yet measured the hearing outcome of this combination, so the additional risk cannot currently be confirmed or excluded.

Yes. Even where a specific variant has not been associated with deafness, BAER data build evidence for your line and support responsible long-term breeding decisions. Visual behaviour cannot reliably detect unilateral hearing loss.

DBE-RE has been directly associated with sensorineural hearing loss in heterozygous cats, although penetrance is variable. Deafness has also been reported in compound heterozygous and homozygous PAX3 genotypes. DBE-CEL and DBE-ALT have not been associated with deafness in heterozygous cats.

PAX3 is a transcription factor involved in the development and migration of melanocytes — the pigment-producing cells of the skin, coat, eyes and inner ear. It acts as an upstream regulator of MITF. Variants in PAX3 can disrupt melanocyte development, producing blue eyes, white spotting and, in some cases, hearing impairment.

Every kitten. A heterozygous DBE parent transmits the variant to approximately 50% of offspring. Parental results cannot confirm which individual kittens inherited it. Each kitten advertised as DBE should have its own genetic test.

Not reliably. Phenotype cannot confirm or exclude a PAX3-associated DBE variant. A cat with blue eyes and white spotting may carry DBE, KIT or both. Show classification records appearance, not genotype.

No. DBE cats commonly show some degree of white spotting. A white, bicolour, harlequin or van phenotype does not prove that blue eyes are caused by KIT alone. The presence of KIT does not prove the absence of DBE.

Yes. Extensive white may result from KIT, from homozygous or compound PAX3 genotypes, or from a combination. Van pattern cannot be used to confirm or exclude DBE.

All currently characterised DBE variants involve the PAX3 gene on chromosome C1. However, genetic heterogeneity has been confirmed — several DBE lineages do not carry any of the four known PAX3 variants, indicating additional genetic causes.

Several. Blue eyes in cats can be caused by PAX3 (DBE), KIT (dominant white and white spotting), TYR (colourpoint/Siamese), and potentially other loci. These are different genetic mechanisms producing a similar visible result.

DBE is autosomal dominant. Only one copy of the variant is needed to produce the phenotype. However, expression is variable — some carriers display blue eyes, while others are latent and show no visible blue.