Intermittent open-mouth locking in Persian cats

This is a condition which I have only just, today, bumped into on the Internet. It’s another inherited condition affecting Persian cats or it’s due to the abnormality of the bone structure of the Persian cat’s head. Although it is very rare. I’ve just written an article about the waning popularity of Persian cats over the past 30 years in the UK as exposed by the 92% reduction in registrations with the Governing Council of the Cat Fancy (GCCF), the premier cat association in the UK. You might like to read that page by clicking on the above link. I discussed the reasons why and on that page to you can see the cat breeds which have become more popular over the past three decades. Health issues are the cause for waning popularity and a lack of health issues or less health issues are the cause for increased popularity on my assessment.

Picture of a concave-faced Persian cat
Picture of a concave-faced Persian cat. Concave: having an outline or surface that curves inwards like the interior of a circle or sphere. Image: PoC based on images in the public domain.
Two useful tags. Click either to see the articles: Toxic to cats | Dangers to cats

Having found one study from 1990 on intermittent open-mouth locking in a Persian cat I searched for some supporting studies. In the 1990 study, they report that “This syndrome has been reported in several breeds of dogs but Irish Setters and Basset Hounds may be overrepresented. As for domestic cats, they state that “It has also been reported in Persian cats.”

Intermittent open-mouth locking in Persian cats
Intermittent open-mouth locking in Persian cats. The headline of the 1990 study referred to in the article.

A study dated September 21, 2004, published on the Pub Med.gov website reports another Persian cat “presented with open-mouth jaw locking”.

And in another Pub Med study dated December 20, 2018, they looked at three cases of open-mouth jaw locking in cats, one of which was a Persian cat. Another was an Exotic Shorthair. As you know, the Exotic is a shorthaired version of the Persian. The Persian cat was a one-year-old 4 kg male, neutered cat. They said that the cause was dysplasia in the temporomandibular joint. The word “dysplasia” indicates an abnormal development, in this instance, of the temporomandibular joint. The temporomandibular joints are those that connect the lower jaw to the skull.

Other studies have said that the open-mouthed jaw locking is caused by laxity in the joints. Taking these two together I take it that at least the major cause of this condition is looseness in the lower jaw due to a congenital defect.

The Vet Lexicon website says that the condition is caused by laxity of the mandibular symphysis. “Symphysis” is the place where two bones are closely joined. This is where the lower jaw is joined in the middle at the front. I don’t know but this looseness in the formation of this joint may cause a commensurate looseness in the joint where the jaw connects to the skull. The lower jaw becomes out of alignment causing it to become stuck in the open position.

The underlying issue, as I read it is that Persian cats have another, albeit rare, genetically inherited health condition which is open-mouth locking. I will take it that the Exotic has the same potential or actual problem. This problem is not discussed however on the Internet.

There is another possible cause: the abnormality of the contemporary Persian cat’s head and face. This may distort the jaw bone causing looseness of the joint where the jaw meets the skull but I am speculating.

The Persian cat is known to have genetically inherited health problems to do with breathing and polycystic kidney disease. The breathing problems come from the selectively-bred brachycephalic head and flat face. The Vet Lexicon website also mentions that the brachycephalic head shape lends itself to open-mouth locking. There are other causes that I won’t go into here because it is to technically medical and I am out of my depth.

The purpose of this post is for it to be a pointer to people who are interested in the Persian cat and who might live with one.

P.S. In this article I am NOT referring to lockjaw in cats caused by tetanus.

Some more articles on genetic diseases in cats are below.

Pub Med studies (2): (1) Symphysiotomy, symphysiectomy, and intermandibular arthrodesis in a cat with open-mouth jaw locking–case report and literature review and (2) Open-mouth jaw locking in cats: a literature review and use of CT in three cases.

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