deaf white cats

[Lady Ten]

So I'm going to keep doing this summary thing because as much as I love messybeast, sometimes it's kind of... well... a mess. I do recommend visiting their pages for further reading, but in the mean time, here's a more concise version.

www.messybeast.com/whitecat.htm

You may have heard that the combination of a white pelt and blue eyes results in a cat that is most likely deaf, but why is this, and how often does it occur? The answer is complicated, as there are several different genes at work here.

First of all, there's more than one genotype that can give a cat a white pelt. Albinism, obviously, is one of these. There are also cases of the white spotting gene covering the cat with white markings. And then you have a gene for a solid white cat ("epistatic/dominant white"), which is the gene associated with deafness.

There's also more than one gene for blue eyes, and if a cat has both the particular eyecolor gene and the dominant white gene (or a lot of white markings around the region of the eyes and ears), the cat has a higher likelihood of being deaf. This is because, basically, blue eyes in a white cat indicates a lack of tapetum, which is generated from the same cells that help a cat be able to hear. It's complicated. The result is that lots of (non-ablinistic) white + a blue eye of a certain genotype = deafness in that ear.

In sum, not all white cats with blue eyes are deaf, but according to messybeast's statistics, of those white cats with one or two blue eyes, 60-80% are deaf; 20-40% have normal hearing; 30-40% had one blue eye and were deaf while 60-70% had one blue eye and normal hearing.

[celestialsquared]

I recently picked up a random feral white kitten two months ago (Bad idea, I know. Good thing she's healthy as far as I can tell) and she's deaf. But she has amber eyes.
Is it possible that white cats in general carry a deaf gene or could this a coincidence?

[cloudbat]

I think white cats in general do carry a deaf gene, it's just more prominent in blue-eyed white cats. Other colorings and eye colors can be deaf as well, it's just less common.

[celestialsquared]

D: I'm kinda glad I picked her up.
She's very energetic and could've gotten in a ton of trouble in the wild.

[cloudbat]

D'awww. I think it was very kind of you.

[Lady Ten]

More or less what Cloud said -- deafness can occur in any phenotype, but white fur increases the likelihood, and white fur with blue eyes really increases the likelihood.

I think I misworded this in my first post, so I'll explain it again. The stem cells that generate pigment (and thus, give color to a pelt) are also responsible for making tapetum lucidum (which is make-you-hear stuff). Depending on the genes involved, white fur can make a cat have less make-you-hear stuff. As I understand it, blue eyes can be a result of a lack of pigment in the eyes, also meaning (for cats) less make-you-hear stuff. A cat with both white fur and blue eyes would have even less make-your-hear stuff. This means that non-albinistic white fur, in some cases, increases the probability that a cat will be deaf, and having blue eyes on top of that compounds that. Here's the statistics on white cats with non-blue eyes: Of the 5% of white cats in the overall population, 60-80% had eyes of other colors (e.g. orange, green). Of those 10- 20% were deaf and 80-90% had normal hearing. So it's less common for them, but still more common than the general population.

(source)

Also I demand to see cute kitten pictures.

[mistytail]

That's interesting! I'm curious though - why doesn't albinism result in deafness more often? Does the lack of pure melanin not affect the production of tapetum lucidum?

I'm pretty glad it doesn't appear tomresult in deafness though. Otherwise we'd have a lot of Helen Kitlers running around.

[Lady Ten]

I'm not sure. Messybeast just says "Albinism is not linked to deafness in cats" and leaves it at that. Apparently albinism in cats is pretty complicated though -- there are five different alleles for it.

[mistytail]

Daaang.

Albinism in general is really complicated though, so I suppose it makes sense. I really should peruse Messybeast more often.

[railroadcrossing]

White spotting seems to damage the hairs in the cochlea either by masking the existing pigments or some other mechanism. Albinism just takes away the pigment.