page_title: Flat-chested kitten syndrome
section_title: Onset and diagnosis
hierarchical_section_title: Flat-chested kitten syndrome / Onset and diagnosis
caption_attribution_description: English: Egyptian Mau kitten with FCKS
context_page_description: Flat-chested kitten syndrome is a disorder in cats wherein kittens develop a compression of the thorax caused by lung collapse. This is a soft-tissue problem and is not caused by vertebral or bony malformation. However lung collapse can be a secondary symptom caused by bony deformity affecting the thorax such as pectus excavatum. In mild cases, the underside of the chest becomes flattened; in extreme cases the entire thorax is flattened, looking as if the kitten has been stepped on. The kitten will appear to go from normal to flat in the space of about 2–3 hours, and will usually then stabilise. FCKS is frequently misdiagnosed as pectus excavatum due to inadequate veterinary literature or lack of experience with the condition on the part of the clinician.
  FCKS is most frequently caused by collapsed lungs. There are numerous causes for lung collapse, and therefore numerous causes for FCKS. One possible cause for flat chestedness that develops soon after birth is atelectasis.
  Causes of atelectasis include insufficient attempts at respiration by the newborn, bronchial obstruction, or absence of surfactant.
context_section_description: FCKS develops usually in kittens around three days of age, and sometimes affects whole litters, sometimes only individuals or part of a litter. Kittens can go flat any time during early maturation, some flattening as late as 10 days of age or (in very rare cases) later. It is possible that the later-developing cases are due to Respiratory tract infection or pneumonia. Until 2010 FCKS was believed to be caused by a spasm in the intercostal muscles, but re-examination of old post-mortem data (i.e. that kittens remain flat even when they are dead and therefore cannot maintain a muscular spasm) and new data has led to the conclusion that flattening is caused by failure of the lungs to inflate normally or, when it occurs in older kittens, by lung collapse. This cause is now cited by the veterinary community (Sturgess 2016) but without any source acknowledgement.
  Gross physical symptoms include flattening of the underside of the thorax in moderate cases (a ridge can usually be felt along the sides of the ribcage, running parallel to the spine); complete flattening of the upper body in extreme cases (the kitten looks as if it has been stepped on); moderate to extreme effort and/or gasping during breathing; the gut is drawn upwards during the in-breath. Breathing is not usually rapid (as in pneumonia or pyrexia) but at a normal rate when compared with unaffected kittens. The position of the thorax and activity of the abdomen is not unlike that seen during normal hiccups, but the sudden spasm in hiccups is slowed down or halted in FCKS: where a hiccup releases, returning the body to a normal position, FCKS breathing does not release. There may be involvement with digestive difficulty in FCKS kittens (see Colic, below).
  Determining whether a kitten has FCKS or not can be difficult with only text descriptions: a mild case of FCKS causes the thorax to feel similar to the shape of a banana when held curve downward. The ribcage is not fixed in position, and the most noticeable effect in mild cases is the ridge along the side of the ribcage.
  The condition causes weight-gain to halt, respiratory distress, inability to feed normally and, in a significant proportion of cases, death. However, since a significant percentage of kittens survive the condition immediate euthanasia is not indicated, and supportive treatments can be employed to increase the likelihood of survival (see Treatment, below).
  The condition is often misdiagnosed as Pectus excavatum, with which it has no direct connection, although FCKS kittens may also have PE. Although the condition is believed to be more prevalent in the Burmese breed it is found in every breed of cat, including non-pedigree domestic cats, and the apparent prevalence in the Burmese is most likely due to better communication between breeders and reporting of the condition, as well as the naturally more barrel-shaped chest of this particular genotype. Since early reporting of the condition identified the Burmese as susceptible the Bengal breed, with a similar physiology, has emerged, and shows a similarly large number of FCKS kittens, however this may be due to specific interest in the condition among those working with the breeds. It is reported in all breeds and in domestic non-pedigree cats, both those kept as pets and those living as 'barn cats'. An article in a Swedish cat club newsletter about FCKS led to a spike in reporting of the condition in Ragdolls in Sweden.
  The syndrome is life-threatening in a significant number of cases (possibly around 40%) mainly due to a lack of understanding of the underlying cause of the condition, failure to treat colic (leading to slow starvation) and insufficient sources of information in veterinary literature.
caption: Egyptian Mau kitten with FCKS
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