This test detects the DBEALT variant of the PAX3 gene, one of the dominant blue eye (DBE) mutations recently described in the cat. A single copy produces blue eyes, often accompanied by white patches on the head or body. The health concern is that the variant is associated with auditory defects, ranging from unilateral to bilateral deafness, with severity that is difficult to predict in each animal. The available data are recent and limited, so the decision to breed with this variant requires information and caution.

Variant recently introduced into British Shorthair programmes from Altai-type lines. Its actual spread in the breed and in other populations is not yet well characterised: limited data.

- Persistent blue eyes in both eyes or heterochromia\n- White patches on the head or coat frequently\n- Uni- or bilateral deafness of congenital onset\n- Absence of response to sound stimuli or abrupt awakening to vibrations\n- Increased vocalisation in cats with bilateral deafness\n- Possible additional effects of the variant under study (limited data)

Dominant blue eyes have historically been pursued in breeding programmes through white cats or cats with a tortoiseshell pattern, with the drawback of the associated risk of deafness. In the 2020s, molecular genetics described several independent DBE variants of different breed origins, including the DBEALT variant of the PAX3 gene, spread from Altai-type cats into British Shorthair and other breed breeding programmes. The association of PAX3 variants with auditory defects became apparent shortly after their spread, prompting the development of specific tests. The full clinical characterisation of this variant is still ongoing: it is advisable to follow laboratory updates.

- Test animals from DBE lines before considering any mating with the variant.\n- Do not mate two DBE animals with each other: homozygotes with a higher risk of defects may be produced.\n- Perform an audiometric study (BAER) on DBE cats before their use in breeding and, where possible, on the offspring.\n- Prioritise auditory health over the blue-eye phenotype: consider programme alternatives with non-carrier animals.

Differential diagnosis of deafness: other congenital or infectious causes (otitis media/interna), senile deafness and deafness associated with dominant white (W) with an all-white coat. The BAER test confirms deafness and its laterality, including unilateral cases not evident on examination. Deaf cats can have a good quality of life indoors with stable routines and visual communication, but should be identified before sale or adoption.

1. Abitbol M et al. (2024) Different Founding Effects Underlie Dominant Blue Eyes (DBE) in the Domestic Cat. Animals (Basel) 14:1845. PMID: 38997957 (define DBEALT)
2. Abitbol M et al. (2024) A PAX3 insertion in the Celestial breed and certain feline breeding lines with dominant blue eyes. Anim Genet. PMID: 38644700 (alelo DBE^CEL)
3. Rudd Garces G et al. (2024) PAX3 haploinsufficiency in Maine Coon cats with dominant blue eyes and hearing loss resembling the human Waardenburg syndrome. G3 (Bethesda). PMID: 38869246 (sordera, alelo DBE RE)
4. OMIA:001688-9685 — Auditory-pigmentary syndrome, PAX3-related in Felis catus.
5. Abitbol M et al. (2025) Dominant blue eyes in Maine Coon cats: New PAX3 variant and updated phenotypic data. Anim Genet. PMID: 40459211 (alelo DBEAGO)
6. Abitbol M et al. (2026) Additional PAX3 Variants for Dominant Blue Eyes in Cats. Anim Genet. PMID: 42728793 (alelos DBENAD/DBEMARU)