Thoracic wall deformity in Bengal cats – Morphological findings and results from a breeder questionnaire

Thoracic wall deformity (TWD) is reported in several cat breeds. The Burmese and Bengal cats appear predisposed, suggesting a genetic background. Thoracic changes in Bengal kittens were investigated using whole-body computed tomography, macro- and microscopic examination of the rib cage. By using a questionnaire, breeding performance and kitten mortality among Bengal cats in Sweden during a two-year period was analyzed. TWD comprised a spectrum of symmetrical and asymmetrical rib cage changes. Macroscopically, lordosis, flat chest and pectus excavatum were frequent findings. When asymmetric, the right rib cage was typically most severely affected. Microscopic rib changes included angled rib cartilages, uneven growth plates, enlarged perichondrial ring of Ranvier, ectopic cartilage formation, fracture of primary trabeculae, and abundant vascular structures in rib cartilages. The questionnaire revealed TWD-affected kittens in 38 out of a total of 311 litters (12%). Mean litter size was 4.0 (SD 1.8). Stillborn kittens and kitten deaths within the first 24 h occurred significantly more often in litters with than without TWD (20% vs. 12%, respectively; P = 0.025). Breeder-reported signs included lack of weight gain and dyspnoea. Male kittens were over-represented (72%). Two thirds of owner-reported kittens affected by TWD survived. The proportion of litters with TWD affected kittens varied between sires. The increased perinatal mortality and proportion of stillborn kittens in TWD-affected litters suggest that both pre- and postnatal factors contribute to TWD. The variation in frequency between sires suggests a genetic background. Strategic selection of breeding animals may reduce the frequency of TWD. Identification of genetic risk variants warrants further investigation.