Flat chested kittens, characterised by a dorsoventral flattening of the rib cage, are well recognised by breeders but are not well reported in the veterinary literature.
Kittens with flat chests have a thoracic deformity that begins cranially around the forelimbs, and is characterised by sharp angulation at the costo-chondral junction causing marked dorso-ventral (top to bottom) flattening of the rib cage. There may be cranial thoracic vertebral kyphosis (ventral deviation of the spine towards the ground) and dorsal deviation of the sternum.
Affected kittens present with clinical signs of:
- Weight loss or failure to gain weight
- Failure to suck from the queen
- Increased respiratory rate and effort
Most kittens remain bright and active unless severely affected. In those kittens that survive, the deformity will become less obvious as the kitten grows and is frequently unnoticeable in the adult although little change in the spinal deformity occurs.
The condition is variable in severity from very mildly affected kittens reported to be flat chested for short periods (hours to days) to severely affected kittens where the prognosis is very guarded. Anecdotal reports suggest there is a heritable component to the condition, but other factors including environmental influences also appear important.
The speed at which changes in the thoracic shape occur, its transient nature (in some kittens) and flexibility of skeletal system in the new-born make it unlikely that this condition is a primary skeletal deformity or connective tissue abnormality. This would tend to suggest that some myopathy involving the intercostal and diaphragmatic muscles may well be involved.