In DBE cats, kittens that inherit and express the variant typically show some degree of white spotting. This may range from large, visible patches to minimal or easily overlooked markings — on the chin, between the toes, or at the tip of the tail. These markers are often subtle, and their extent is variable rather than fixed.² ⁴

The currently characterised DBE variants all lie within a single gene, PAX3, on feline chromosome C1.¹ ² ³ ⁴ Other, as-yet-unresolved DBE lineages may have a different molecular basis, but this has not been established.

DBE does not exist in isolation. PAX3 belongs to a family of genes governing the development, migration and survival of neural-crest-derived cells, including melanocytes. Variants affecting this pathway produce comparable pigmentary — and sometimes auditory — phenotypes across many species, including mice, dogs, horses and humans.³ In mice, variants in the PAX3 homologue produce the classic Splotch phenotype, and in humans, PAX3 variants cause Waardenburg syndrome types 1 and 3.³

Waardenburg syndrome is named after the Dutch ophthalmologist and geneticist Petrus Johannes Waardenburg, who first described it in 1951. In humans, PAX3-associated Waardenburg syndrome is defined by features that can include pigmentary changes of the iris, skin and hair, and congenital sensorineural hearing loss.³

This illustrates an important point of perspective. Many of the same genes that produce recognised coat colours or eye colours in domestic animals are described, in humans, as "syndromes" or "genetic disorders." The underlying biology is shared; the framing differs. For example:

• ASIP — in mice, variants produce the yellow, obese agouti phenotype; in cats, ASIP governs normal tabby (agouti) banding of the coat.

• TYR — in humans, TYR variants cause oculocutaneous albinism with increased skin-cancer risk; in cats, the same gene produces the colourpoint and albino series.

• KIT — in humans, KIT variants cause piebaldism and are implicated in certain cancers such as gastrointestinal stromal tumours; in cats, KIT produces white and white spotting.

Framed this way, DBE is not an exotic anomaly but one variant within a well-characterised family of pigmentation-related genes shared across mammals.

Note: the founder histories below (names, dates, cattery origins) come from breeder and community records. The genetic findings are drawn from the peer-reviewed literature and are cited accordingly.

DBE-ALT (Altai)

According to breeder records, blue-eyed cats were noticed among street cats in Ust-Kamenogorsk, Kazakhstan, in the mid-to-late 1990s, and were used to develop the Altai line. Community sources name early founders including a semi-longhaired cat with odd eyes (one blue, one yellow-green) and a black cat, Fyodor, with a blue eye and a white tail-tip — a phenotype compared at the time to the American Ojos Azules. The dominant blue-eye trait in these cats was inherited dominantly but not always visibly expressed.

The trait was later characterised genetically. DBE-ALT is an RD-114 LTR insertion in intron 4 of PAX3, associated with DBE in Altai cats and several other lineages, and consistent with autosomal dominant inheritance and incomplete penetrance.²

To date, three homozygous (RD/RD) DBE-ALT cats have been reported: two in the Altai line, described by their breeder as hearing (though no BAER testing was performed, so unilateral deafness could not be excluded), and one in the Nanotigr line, reported deaf by its owner. All three were white or almost white.²

A prominent white tail-tip — sometimes extending over part of the tail — is often described by breeders as characteristic of Altai-line cats. This is a breeder observation rather than a documented diagnostic feature.

DBE-CEL (Celestial)

The variant now designated DBE-CEL was previously grouped by breeders together with the Altai gene. It was characterised in 2024 by Prof. Marie Abitbol and colleagues and shown to be a distinct variant, separate from DBE-ALT.¹ ²

DBE-CEL is a FERV1 LTR insertion in intron 4 of PAX3, showing autosomal dominant inheritance with variable expression and incomplete penetrance.¹ In the studies to date it has not been associated with deafness, and affected cats did not show dystopia canthorum — a facial feature seen in the PAX3-associated forms of human Waardenburg syndrome.¹ ²

As the authors report, dystopia canthorum was not observed in adult DBE cats from the Altai, Celestial, British, Sphynx or Siberian backgrounds, and the DBE-CEL variant found in the Celestial breed was not associated with deafness.²