Breed-related disorders of cats
1. Danièlle Gunn-Moore, 2. Claire Bessant, 3. Richard Malik
Journal of Small Animal Practice, Volume 49, Issue 4, pages 167–168, April 2008

Quotation from this article:
Unfortunately, not all defects have been propagated inadvertently. Many actually define particular breeds. Some of these defects are esoteric genetic mutations that generally have little impact on overall health, such as the hair follicle defect that gives Devon Rex cats their short fragile curly coat, and the acromelanosis that causes Siamese and Tonkinese cats to have “points” (temperature dependent melanin formation). However, other breeds are defined by genetic mutations that actually have substantial adverse impact on overall health and longevity. For example, Manx cats have a lethal autosomal dominant gene for the Manx mutation that results in a short or non-existent tail (sacrocaudal dysgenesis) and a variety of secondary abnormalities including constipation, megacolon, rectal prolapse, congenital urinary tract defects, incontinence and spina bifida (Robinson 1993, Howell and Siegel 1963). Other examples include Sphynx cats with their baldness which puts them at risk from sun burn and chilling (depending on the weather), Munchkin cats with their chondrodystrophic shortened limbs and associated osteoarthritis, Persian cats with brachycephalic upper airway issues, and Scottish Fold cats as described in the paper by Takanosu and others in this issue of JSAP (see page xx). This paper confirms the deleterious nature of this autosomal incompletely dominant gene that results in the forward folding of the ears.
 

When studying the literature list of this article, where to find the corresponding literature to these defects, which unfortunately have not been propagated inadvertently, and many of them actually define particular breeds, one may notice the following: 

Manx cats

• The Manx is a breed, which appeared naturally and which still can be seen on the Isle of Man. The propagation of the Manx on this island was not specifically directed by man, it was inadvertent.
• The literature, mentioned in this article, is not quite actual.
• Are there statistics about the average life expectancy of the Manx - that the Manx does not become so old because of the taillessness?
• Are there statistics that the lack of the tail has a significant adverse impact on the health of the Manx - how high is the percentage of Manx cats, which are impaired in their health?

Munchkin

• No quotation of literature that the Munchkin is at risk to acquire osteoarthritis because of its shortened limbs, caused by chondrodystrophy (as this article states!).

I had to look into a medical dictionary, what chondrodystrophy is:
"die v.a. genetisch bedingten (endogenen) Störungen der enchondralen Knochenbildung (Ossifikation) u. damit des Längenwachstums des Knochens, bei ungestörtem Dickenwachstum." Roche, Medizinisches Lexkon, 5. Auflage, online
the endogen disruption, in particular genetic, of the enchondral building of the bones (ossification) in association with the disruption of growth of the bones' length together with undisrupted thickening of the bones.

One has to put the following questions to such an article:

• a) Has the research of the shortened limbs of the Munchkin already come to an end = final conclusion?
• b) Has the research of the growth of the length and building the bones in the Munchkin already come to a final conclusion?
• c) Are the limbs of the Munchkin - also the bones of the limbs - in fact thicker than in other cats?
• d) Are there statistics about the average life expectancy of the Munchkin - that the Munchkin does not become so old because of its shortened limbs?
• e) Are such statements also made on the dachshund (which is used for hunting) - and thus giving the advice not to breed the dachshund?

Probably also the breeds, resulting from crossbreeding with the Munchkin, are also included in this article.

Sphynx

• No literature for the statement that the Sphynx are at higher risk from sun burn and chilling.

One has to put the following questions to such an article:

• Are there statistics about the average life expectancy of Sphynx cats - that the Sphynx does not become so old because of its baldness?
• Are there statistics that the health of the Sphynx is significantly more impaired because of the lack of hairs than of cats with hairs?

To the "story with the sun burn":

Kimura T, Doi K: Dorsal skin reactions to sunlight and artificial ultraviolet light in hairless descendants of Mexican hairless dogs.
Exp. Anim. 44(4), 293-299, Oct. 1995
page 299:

"Histologically, as reported previously (1994), the dermatological characteristics of hairless dogs are obviously different from those of nude mice and other hairless animals.

In conclusion, it was clarified in the present study that the degree of severity of dermatological changes in hairless dogs depended on the kind of UV light source. That is, solar exposure provoked remarkable pigmentation while artificial UV irradiation brought about severe sunburn reaction in the skin of hairless dogs."

May this conclusion also be applied to naked cats that their skin differs from the skin of naked mice?

To the remarkable statement, cats without hairs have problems to adapt to climatic changes, let's have a look, from where the naked cats are coming:

• The Mexican Hairless comes from New Mexico, USA.
• The Sphynx comes from Toronto, Canada, Oregon, USA, Minnesota, USA.
• The Don Sphynx comes from Rostov-na-Donu.
• The Peterbald comes from St. Petersburg.

The climatic conditions could not be more different.

Please read the article about naked breeds in katzenzeitung.eu.

Probably also the Don Sphynx and Peterbald are included in this article.

General remark to such articles

This article is written, showing a clear tendency, when such words are used like "inadvertent", "unfortunately", or "genetic mutations that actually have substantial adverse impact on overall health and longevity".