Flat Chested Kitten Syndrome (FCKS)
This text is placed here to help breeders and owners who may come in contact with this distressing condition. Please note, I do not have veterinary training: the information here has been gathered from experience, both my own and that of a very wide group of breeders, and the information learned through communicating and bringing together what we have learned.Several websites and resources have copied the information, or earlier versions of it (with permission), but this is the most up-to-date version, since it is informed by discussion on the breeder support group and other sources of information.
Because of the quantity of information that I have gathered, and because I don't believe in excluding anything I have learned, there is a lot to read. I have divided this up under headings, but I would strongly advise you to wade through the whole thing, so that you don't miss anything essential. The sections follow on from each other and are not intended to be read out of context.
The Treatment page is separate: please see the link on the sidebar.
Where this information comes from
You are welcome to print, download, distribute or reproduce this information, however, you must acknowledge the source (give the URL), the name of the author, and the 'warning' that I am not a Vet to ensure people reading the information are not misled. For information prepared by a vet, please use the veterinary article linked below. Since most vets will not consider anything on the internet to be useful, you will get a far better response to treatment suggestions if you take this article, prepared by our veterinary advisor, to your surgery.
For a clear, brief description of FCKS please read my article on Wikipedia.
I have gathered information from breeders who have experience of FCK to pass on to those who suddenly find themselves confronted with it and I now have a fair amount of information on how to deal with it, so I would like to acknowledge all contributions from breeders and vets. I have made a large number of updates recently, so there is quite a lot of text to wade through. This page is NOT a criticism of breeders or breeding - no good breeder will knowingly breed kittens who will get FCK. If you have a litter, or a kitten with flat chests please contact me as soon as possible, preferably the day (or night) that the kitten goes flat, as the sooner I hear from you the sooner I may be able to help. I would be very grateful to receive any and all information on your litter as this will add to the body of data available to help others. The sub-page on this subject is very long, because I am trying to pass on as much as possible of what I have learned about this condition. I don't believe you can have too much information about this, but I'm sorry about the length!
Support Group
The list is open only to those dealing with FCK directly, and membership is moderated to make sure that it remains a genuine support group. You can apply to join by following this link, clicking on the 'join this group' button on the page you reach, and logging in, or creating a login account with Yahoo groups at the prompt.
For vets
FCKS (.pdf)
FCKS and Pectus Excavatum (.pdf)
Please let me know if these links are broken.
FCK= Flat-chested Kitten; FCKS = Flat Chested Kitten Syndrome
NB There have been some breakthrough treatment ideas for this condition. These are discussed below - please let me know if you use these treatments with success (or otherwise). This web page owes a great deal to the sharing of information by breeders worldwide, and if we can find a way of treating kittens with the problem it will be due entirely to the generosity and time of those who have responded to this web page.
Information downloads to print
article download (.pdf)
The same article but including a section on Pectus Excavatum as vets frequently misdiagnose FCKS as PE.
article download (.pdf)
Please let me know if these links are broken.
What is FCK or FCKS?
FCKS is caused by collapsed lungs (and NOT as formerly believed, by a muscle spasm) and the medical term for this type of partial collapse is atelectasis. It is likely that all FCKS kittens are suffering from varying degrees of atelectasis, since even severe cases continue to breathe, so the lungs are not completely collapsed.
Causes of atelectasis include insufficient attempts at respiration by the newborn, bronchial obstruction, or absence of surfactant (a substance secreted by alveoli that coats the lungs and prevents the surfaces from sticking together). Lack of surfactant reduces the surface area available for effective gas exchange causing lung collapse if severe. There can be many reasons for atelectasis in kittens, but probably the commonest cause is prematurity.
Unlike human babies, kittens are born very immature: blind, deaf, the intestinal tract not fully developed etc., so even slight prematurity may tip them over the edge from being viable to not viable. Many FCKS kittens may have fallen just the wrong side of this boundary in their development at the time of birth. Further, if a kitten does not scream or open its lungs well enough at birth, even if it is fully mature and has sufficient surfactant, it may end up with atelectasis. Patches of atelectasis in the lungs mean that part of a lung is not operating properly. If the kitten goes to sleep and its respiratory rate drops, the patches of atelectasis can slowly expand until large areas of the lung collapse and cannot be reinflated. Good advice to any breeder therefore would be to ensure that kittens cry loudly when they are born, to make sure that the airways are clear, but also that the lungs expand as fully as possible. (This was the reason newborn babies were always held upside down immediately after birth (so that any residual fluid drains downwards) and smacked to make them cry strongly.)
Most kittens suffer from congenital 'secondary' atelectasis, which presents shortly after birth. There have been no reports of kittens born flat (primary atelectasis). Pressure from outside the lung from fluid or air can cause atelectasis as well as obstruction of lung air passages by mucus resulting from various infections and lung diseases - which may explain the development of FCKS in older kittens (e.g. 10 days old) who are not strong enough to breathe through even a light mucus, or who may have inhaled milk during suckling.
Tumors and inhaled objects (less likely with kittens, unless their bedding contains loose fluff) can also cause obstruction of the airway, leading to atelectasis. In an older cat the intercostal muscles are so well developed, and the ribs rigid enough that the ribcage will not flatten if the lung collapses: in kittens the bones are much more flexible, and the tendons and muscles more flaccid, allowing movement of the thorax into abnormal positions.
Congenital newborn atelectasis would not be unusual in a very large litter of kittens (such as 10), where the size of the litter may lead all the kittens to be small and mildly underdeveloped.
Although the veterinary term 'Pectus Excavatum' is sometimes used for FCKS (Flat-Chested Kitten Syndrome), this is inaccurate. Pectus excavatum refers to the sternum (breastbone) growing pointing inwards into the body: a few Flat-chested kittens also have pectus excavatum, but many do not and a flat chest is not the same thing as an ingrowing sternum. I am very grateful to one of the breeders who read this page for sending this x-ray of pectus excavatum:

In FCKS the underside of the ribcage flattens and sometimes caves in. I believe that the majority of cases of FCKS go undiagnosed: when the condition is only mild the kitten does not show any signs of distress or weakening and can thrive as a normal kitten. The ribcage will right itself with time. A mild case of FCKS probably requires no intervention, although supplementing with vitamins and - if the kitten is one of a large litter - with additional milk, is highly advisable to prevent the condition from worsening.
Usually in extreme cases the kitten will start gasping for breath and will die if left. Sometimes the flattening does not
cause breathing difficulties and the kitten can survive. Once the ribcage is pulled inwards though, there is a danger of lung damage, and some kittens who appear to do well at first nevertheless die, and autopsy has shown abnormal lung tissue. The two diagrams below were produced in a veterinary study that was commissioned by the Burmese Cat Club (details further on).
With the flattened chest of a FC kitten, the muscles between the ribs (intercostal muscles) and the muscles of the diaphragm cannot open and relax correctly; the whole volume of the chest cavity is decreased because the lungs are not properly inflating with each breath. Less oxygen is able to get to the muscles and the kitten tries to get the extra oxygen by breathing faster -- i.e. it appears to be panting.
How can I tell if my kitten has FCK?
It's very difficult to explain what a flat chest feels like in words, but if you can get hold of a reasonably fresh banana (yes, a banana) you can feel what a flat ribcage is like: I've cut this one in half so that you can see the shape in cross-section. Hold the banana with the flattest side downwards (usually on the inside of the curve). Hold it as I've illustrated, and draw your hand upwards. You can see that the outside of the skin has two clear ridges at the lower edge, and the bottom is flatter than the sides and top. This is almost exactly what a mildly flat chest feels like (even down to the size) only with a covering of fur
You may feel a slight ridge running along the ribcage in some kittens that does not progress into FCK, so don't panic!
Normally the flat chest is simply that: flat. But if the muscles of the diaphragm are severely affected they will pull the sternum into an abnormal position -- i.e. the sternum will be pulled into the chest cavity, and this in turn will distort the shape of the heart and prevent the lung tissue from developing normally. This pulling in is one reason the condition is sometimes called pectus excavatum, but usually the sternum does not grow inwards, it is pulled in with the ribcage. When this happens recovery is unusual.
This kitten has an inverted sternum - you can clearly see it is dipped into the body instead of curving outward.
There is another condition (independent of FCK) in which the sternum sticks out, and though this apparently has no health implications, it is considered a veterinary fault
The kitten was a single FCK in a healthy litter, and was losing weight and clearly failing until he was put onto supplement feeding with KMR. He is now happy and healthy, though his sternum has not righted itself. He is smaller than his siblings.
(many thanks to his owner for sending his picture and regular updates on his progress)
[if you have photographs that show FCK it may be useful to other people to be able to see them - I would like to put them here if they show the condition.]
There are degrees of flat-chestedness -- sometimes occurring in the same litter. Many slightly flat-chested kittens go unnoticed and recover on their own. Various causes have been put forward for this condition developing: The Burmese Cat Club funded research into Taurine deficiency which, though it only had a very small study group to work with, concluded that it was not relevant. I have scanned the pages, and images of the article can be downloaded here (click on the filenames on the list to download them). I apologise if this infringes any copyright, but the article was printed some years ago and is difficult to obtain now, and I feel that providing information to save lives must outweigh copyright concerns. Other theories have suggested Potassium deficiency, but treatment with potassium supplements as suggested by Bristol Veterinary College have not shown significant results in treating the condition, and blood samples have not suggested a deficiency. There has been no long-term or serious study into this condition, and for this reason I am assembling data for the future so that if such a study is undertaken a sizeable sample of litters can be studied to gain more information.
See below in 'Treatment' for information about Taurine used to cure FCKS.
Rex kitten with FCK - note also the dip in the spine just below the shoulders
Egyptian Mau with FCK - note splayed elbows pushed out by the sides of the ribcage
Which breeds are affected?
An observation I've made through breeding both Burmese and Siamese (and Tonkinese): one of the earliest signs of flattening is the ridge that you can feel on the sides of the chest. I felt this several times in Siamese kittens, and I began to wonder if there isn't a natural period during the early days of development when the ribcage tends to change shape, causing this ridging. Comparing the shape of the ribcage of the Siamese and the Burmese, it was immediately obvious that the normal Burmese ribcage is a completely different shape, being naturally rounder and flatter. Thus I wondered if the apparent over-occurrence of FCKS in this breed has less to do with the genes and more to do with the fact that the kittens start out with a much more flat shape. The Siamese who showed the ridging never went flat, but their ribcages were very deep and narrow, and flattening would have been much more difficult; plus the natural tendency of these cats would be for the ribcage to deepen. I suspect therefore that mild flattening is quite commonplace across all breeds, but rarely noticed, whereas mild flattening in Burmese and similarly-shaped breeds like the Bengal is actually more serious because they are already 'flat', and therefore it is a) more often noticed and b) more often affects the kitten. If a kitten is slightly flat it will start to have difficulty in breathing and feeding, and that would probably make the condition worsen, whereas a kitten who it is not troubled by the flattening will feed and move normally and the condition will naturally go away, possibly without ever being noticed.
Will my kittens die?
Sadly, if your kitten survives the 10-day and 3-week times this is not a guarantee of future survival. Kittens who are particularly small have often got a compromised heart and they can die at 12-18 weeks, or even later. We all become very attached to these little surivors, and it can be heartbreaking to think you have saved them and then have them die on you just when you think you are out of the woods. There are no guarantees I'm afraid, but if the kitten is a normal size by 16 weeks and seems normal in every way, then it probably is OK.
Is FCKS sex-linked?
Since both sexes get FCKS the likelihood is that the preponderance of male kittens suffering from it is related to relative size and weight, and that it is not sex-linked. Possibly, if we ever get enough data about the problem, and can raise funds to do a veterinary study, it may be worth examining something like testosterone levels in affected and unaffected kittens.
What can I do about FCK? TREATMENT
This section is long and quite detailed, so I have put it in a separate section to make it easier to navigate and display.
Correct diagnosis - types of FCKS
Nutritional support and drugs
- Nutrition
- Vitamins
- Taurine
- Antibiotics
- Steroids
Splinting
Acupuncture
Oxygen
Please click here to go to the TREATMENT page.
Hills a/d - a warning
Why did this happen?
Some lines throw FCK far more than others, and some studs or queens are well known for it, and so you avoid them in your breeding lines if you can. Virtually all studs in all breeds have thrown one at some time or another (because of the numbers of kittens they sire), so it's unavoidable, and abandoning ALL lines that have thrown FCK would be incredibly damaging to any breed as it would limit the gene pool far too much. It seems that either sire or dam, or both, may carry the genes that trigger the condition, but having it manifest in a litter of kittens can rely on combinations of environment (whether the queen is healthy and produces a lot of milk) and other factors. The main thing to avoid is having a known serious FCK carrier in your pedigrees, but also to avoid having the same cats in the pedigrees too much as well. FCK appears much more often with inbred lines. There is a dramatically increased link of FCKS in litters from related parents, and one of the reasons the condition may be particularly prevalent in Burmese is the extremely limited gene pool of this breed.
There is also no doubt in my mind that sometimes FCK appears without any apparent genetic component. I suspect that it is a condition that manifests as a result of any number of causal factors. This is a bit like a human running a temperature: we get a temperature as a result of a huge number of illnesses, but the temperature is always the same, and it is just a sign that something is wrong, and is caused by an underlying illness. It looks as if single cases of FCK can appear a bit like a temperature - the outward sign of something being wrong, so it can be the result of another problem, as well as a problem in itself.
Unfortunately, some stud owners continue to run studs who have thrown a lot of complete litters of FCK kittens. I have personal experience of a stud owner who said categorically that her cat had not thrown any, only to find after my kittens were born that he had had two complete litters and the stud owner knew about them: I talked to the owner of the queen that had had these kittens, so there was no question of the information being just malicious gossip. This stud was widely used as he was a UK Grand Champion: when 'clean' lines were mated to him the kittens were generally healthy, but kittens bred from those offspring nearly always develop FCK. Fortunately my kittens were all completely healthy, but I knew that they had at least a 50/50 chance of carrying FCK, and so I did not feel I could keep a kitten from the litter to continue my lines. I was very sorry to lose this line, as this unwitting 'test' mating showed that my line was not susceptible to FCK. Unfortunately I could not mate the queen again to get a breeding girl from her, and she had to be neutered. Needless to say, I was more angry than I care to remember!
It seems that there are numerous genetic markers that must be present in order for the condition to arise in unrelated matings: if a cat has many of these markers then most of the offspring will have flat chests. If mated to another cat with a high level of markers, then all kittens in a litter will be flat. Single flat kittens may suggest that one of the parents carries a significant number of markers that were mitigated by the other parent being relatively free of them OR that there is an environmental rather than a genetic reason for the condition developing.
FCK can be affected by the situation of the queen: any adverse event during pregnancy (including poor nutrition) can render a queen liable to produce FCKs if she carries a small number of 'markers', while a better environment may prevent the condition from developing. If you have just one flat-chested kitten in a litter then the causes could be environmental more than genetic (see paragraph below), but maybe using a different stud would be safer for breeding next time. It seems to be rare to get a whole litter of flat chests unless both parents are strong carriers of the genetic cause, so it would be advisable to abandon a breeding line that produced whole FCK litters. Single flat kittens in a litter, though indicating a risk in the lines, may not be such a serious problem and it may be only one parent who is the cause, assuming there is no environmental factor. Many breeders prefer to avoid any incidence of FCK in the lines they are using if they possibly can, even though this may severely limit their gene pool (and there are many dangers for a breed in following this course), but sometimes a kitten will turn up in a line that was thought to be clear. It is a matter for each breeder to weigh up the factors of FCK risk and limiting their gene pool to a dangerous degree, and I'm not going to criticise the decisions individual breeders make.
There may possibly be physical reasons why FCK may occur that have nothing to do with genetics or the bloodlines: if a queen was ill during pregnancy, or had to have antibiotics; if the queen had a fall during pregnancy that might have knocked one of the fetuses. Also, if one kitten is getting less good milk than the others: sometimes a queen has one teat that does not produce as much milk as the others, and the kitten who gets this teat may go flat from vitamin deficiency or lack of good nutrition (if that is one of the causes). Sometimes with very big litters the smallest may be flat, though I have had litters of 8 and 9 with no problems at all (and the queen lay on top of the radiator all through every pregnancy without producing a single flattie), so I'm not sure that is a legitimate cause. Some people will look for any excuse to say it's not their bloodlines, particularly if the cats they breed are very good show quality, or if they are very attached to their bloodlines for other reasons. All you can do is ask the breeder if you are looking for a stud or breeding queen. FCK CANNOT be caused by your queen sleeping on a heat pad or other heated surface while pregnant. I have had 15 Siamese, Burmese and Tonkinese queens over the years who have spent their entire pregnancies (to various studs) stretched out along the tops of radiators or sitting on top of an AGA, and never had a single flat chest. Veterinary studies have now comprehensively RULED OUT sleeping on heated surfaces as a cause of FCK, though originally when the syndrome was first identified it was suggested that it might be one possible cause.
How can I prevent or avoid this condition?
Unfortunately we really don't know enough either to avoid the condition entirely or to cure it successfully every time (unless the new ideas I've written about above turn out to be successful): very bad cases where the kitten begins to have trouble breathing are unlikely to be cured, and the kitten usually dies. Mild cases can often recover with no help at all, sometimes remaining slightly flat, and sometimes the ribcage goes back to normal. Either way, you must not breed from that kitten, and it's not advisable to breed from any of the litter mates in case the cause is genetic. I would not advise the the repetition of a cross that had produced an FCK kitten again just in case the combination of the two lines was the cause; maybe another stud would produce a safer outcross.
Main things to avoid to try and prevent the occurrence of FCK:
1. Use of ANY antibiotics or medications during pregnancy or nursing
2. Inbreeding in the pedigrees between the male and female lines
3. A Queen who does not produce a good milk supply (if unavoidable, then supplement, even if the milk is coming OK)
4. Using lines known to have produced FCK kittens - though beware, not all breeders are truthful about this
5. Poor nutrition during pregnancy and nursing: plenty of fresh high-quality food must be available to the queen at all times, and raw meat such as rabbit is an ideal source of good nutrition.
If you are reading this because you have a litter with FCK in it I wish you the best of luck, and I hope that your kittens survive. It is heartbreaking to watch babies die, and everyone who has experienced FCK would offer you their support in dealing with it. Unfortunately nearly every breeder who has been breeding for some time will have experience of FCK, if you haven't, then you're very lucky.
Should I buy a kitten with FCKS?
- is the same size as its siblings
- is active and energetic
- has no detectable signs of illness or deformity (e.g. a heart murmur or kyphosis) other than a flat chest
If the kitten -
- is significantly smaller than its siblings
- does not play as actively as the other kittens
- has any other condition in addition to the obvious flat chest
The most immediate problems you should encounter are when it comes to neutering. The heart, though it sounds OK, may be slightly damaged, and that means that spaying/neutering, when the cat needs a general anaesthetic, is a risk time. Talk to your vet about it if you are in doubt, provide him/her with the information leaflets from this website, and take every precaution possible before and during surgery (e.g. risk-minimizing anaesthetics such as Propofol/Rapinovet; full anaesthesia with intubation rather than just 'injection' anaesthetic; pre-operative anti-histamine to guard against vaccine reaction; a veterinary nurse monitoring the heart with a stethoscope throughout the operation (a heart monitor does not pick up on changes in heart sound, only a faltering or erratic beat, by which time the damage has been done). All these things may be more expensive, unless your vet (like mine) does all these things as standard, so be aware of this before you buy the kitten). If the cat comes through neutering fine (and most do), then you should not have any more unusual expenses that you would not have with any other cat.
A 'flattie' is special: it will have had extra special love and attention from its breeder, and will probably be a much more affectionate pet as a result. The breeder may also feel much more attached to the kitten, and will look for a special home for him. If you are prepared to give one of these special kittens a home, then you will be a special owner too.
Links
There are no available veterinary studies on FCKS, but humans also suffer from this condition, and Pectus Excavatum, and there are a number of very revealing sites. The most useful one we have found links the condition to Rickets, and is very well worth consulting. You can get to it here: CTDS information. Check out the link to PE and Rickets, and the one to Zinc, which we feel is very relevant to FCKS.
Max's house - an excellent veterinary-driven site with superb information about nutrition and many veterinary conditions. The section on Tuna nutritional values is particularly useful in reference to zinc and other vitamins identified as possibly relevant to FCKS
Information about a kitten who had surgery to correct pectus excavatum can be had here, with the veterinary information here. The owner says the only thing they would change would be the frequency of bandage changes - this needed to be done more often. There are other sites about pectus surgery on cats where you can direct your veterinary surgeon, and you can find them by searching on google for 'pectus excavatum cat surgery'.
What can I do to help?
The THINK Project is a research group founded to raise funds and collect data in order to create an academic research post to investigate thoracic deformities in kittens, particularly FCK. The website is: http://www.think-project.org/
Our aims are:
Identifying specific thoracic deformities clearly
Informing the public and vets on identification and treatment
Funding multi-disciplinary approaches to researching the problems
Identifying causes with an aim to prevention and treatment
The organisation was launched formally at the GCCF Supreme Show in the UK in November 2005, and you can support it at any time by joining or making a donation via PayPal. download the THINK project information leaflet here. You can also help by completing our questionnaire (you can find it on the website, which was created with the help of a veterinary epidemiologist. We need information about litters with FCK AND litters that are healthy, so that we have a large body of research and control data. Any data sent to us is treated with full confidentiality, and you do not have to give your name or other details unless you want to.
It is likely that at least £300,000 will be needed to fund this research adequately (salary, overheads, consumables, lab and bench fees etc.), and we cannot expect to find all of this from veterinary sources. Initially we will need funds to gather primary data and organise a program of education through vets surgeries, as well as bringing the scheme to public attention. If you would like to make a donation to the fund it will be possible to do so through PayPal (any currencies) - e-mail address is think.project@gmail.org - or by sending a cheque (GBP only) to the treasurer. All contact details are available on the THINK website: www.think-project.org.
Copyright © 2009 Julia Craig-McFeely
This text may be copied or reproduced without permission in newsletters and other information sheets for cat owners and breeders, as long as it contains the name of the author, the original source (the URL) and also the note (given at the top) which must be shown prominently that the author does not have veterinary qualifications. This is to ensure that users of the information are not misled.