Hi, and sorry about the delay, internet is NOT always accessible!
FCK is one of many developmental aberrations in the skeleton of unknown aetiology as the books say. From what you describe you find a small spinal deformity associated with a slightly flattened chest, which is a "usual" combination and well done to find it!
Unknown aetiology is just that: no definite cause of the condition is found, but lots of factors have been associated with it, one is taurine. Whether this is the final answer remains to be seen, what is certain, though, is that lack of diverse essential elements in diet may cause deformities.
There is no definite genetic cause defined, except that some developmental stage has been affected, and that always involves genes. To me, the fact that all these different structures usually develop normally is more of a wonder than the occasional deformity!
I can only say that for the affected kitten, clinical status and development is important, and you absolutely seem to have that well in hand. I´d call it a finding that sometimes occurs, and which MAY be influenced by external/environmatal factors: for instance, if you give albendazole to an ewe at pregnancy day 17 the lamb will be born with a shortened mandible. Usually...
That is why medication during pregnancy is treated extra carefully, and exposure to environmental contaminants and toxic factors we usually don´t have to worry overly about should be avoided, the repair mechanisms do not have time to work on a foetus. It does take only 63+ days to "make"a kitten, which is pretty miraculous in itself!
As it´s gotten past four weeks and is healthy, there is no reason to see it as other than a healthy kitten. And I´d not worry about it being an inherited trait, it´s just something that sometimes happens.
p
