I was thinking of this idea while looking at different in-game mutations. This happens to different animals and humans, and I decided to throw out my idea. We already have extra limbs so why not..

Missing Limbs

Of course this affects animals and humans in a negative way, and typically in cats it's two limbs they're missing.
This mutation could go a few different ways:

A. The adolescent/adult won't be able to hunt due to their deformity.

B. The cub will not be able to train

C. The game can introduce prosthetics that cost SB/GB that can help the cub, adolescent, or adult live normally.

Now, I don't believe this is a lethal mutation in real terms because it's not necessarily as affecting as a Cleft Palette would be, but it's still a mutation.

To make this more interesting, I'd also like to throw out the idea of a random amount of limbs missing, preferably two.

For example, right front leg, left back leg, or even just one back leg. This can vary this mutation different ways so then there's different versions of it you could get. :)

I'd love to hear the criticism and opinions you guys have on this.