You can help - read on...
Since putting this information on the web, I have had numerous enquiries from breeders who have had kittens develop this condition. I'm afraid I don't have any perfect answers, but I can pass on what feedback I've had regarding results and possible causes. This is a very sad thing to experience - we all want our babies to be perfect, and having things go wrong is heartbreaking. For most of us, the worst thing about sickness in a kitten is sitting and watching and not being able to do anything to help. Some vets believe that the condition is due to a vitamin deficiency, and the most commonly used vitamin supplement for kittens is Abidec. This is a liquid vitamin supplement for babies and toddlers available from an ordinary chemist (unfortunately it tastes disgusting). If in doubt ask your vet. Remember that these kittens are always very young and small, so any treatment is very difficult. You only need one drop of Abidec per kitten, so don't end up squirting it down their throats so that they choke. I have used Nutri-drops in a very mild case, and that seemed to help - Nutri-drops (available in the UK, and possibly elsewhere under a different name) is mainly glucose and vitamin A, and a cocktail of other vitamins. It will give a kitten energy to suckle more, which is helpful if your kitten fights against a hand-fed milk supplement.
One thing that everyone also recommends is to supplement-feed affected kittens with a very high-quality kitten milk supplement, even if they seem to be feeding OK from the mother. One breeder observed that FCK kittens seem to use far more energy than normal ones just to keep up, and this has been confirmed by Kit Sturgess, so it is reasonable to expect that the kitten would need supplementing.
Cimicat doesn't seem to be much use as it's not very rich, and I would only recommend KMR which is a marvellous creamy-rich milk substitute, and has saved the lives of countless kittens who did not thrive on Cimicat, regardless of whether they had FCK syndrome. In the UK the supplier is KRUUSE UK Ltd, tel 01977 681523. They have always been very helpful and will despatch the powder to you the same day if they can. I'm afraid it's not cheap! Your vet should also be able to get it for you. You can also get it from CANINE CHEMISTS Tel: 0870 225 4777 (thanks to Doris for sending me the details). In the US, KMR is available at the chain PetSmart. The US distributor is PetAg Inc., 255 Keyes Avenue, Hampshire, IL., 60140; 1-800-323-0877 (Many thanks to Don for this information).
The other alternative is evaporated milk (brand name Carnation in the UK) diluted with water (about 1 part Carnation to 3 parts water) with a raw egg yolk beaten in (as long as you are happy that your egg supply is free from Salmonella). This is VERY nutritious if you can't get KMR. I'd supplement often to make sure the kitten is getting enough nutrition, as we still don't know if poor nutrition from a poorly functioning teat could be a causal factor. The exercise of struggling against you (at first) and of suckling from a syringe will also help the lung development, but will also tire the kitten, and you may have to abandon hand-feeding if it is counter-productive because of exhausting the kitten.