Sorry folks, but inbreeding is inbreeding, regardless of the animal. To get an animal with a deformity it would take nothing but a mutation to arise in one animal and then that animal's offspring that received said gene to breed with eachother or with the parent that had the original mutation. Does it happen all the time? Obviously not, but it is still a very real possibility. It's a matter of how genetics work, not what species you're inbreeding.