Peripheral Artery disease

This disability makes blood vessels thinner, which limits the blood flow to limbs and causes pain when walking.

Jawless

This would be a fatal mutation and the cub would die in a few days from starvation. This means that the cub is born without its jaw, which means it wouldn't be able to suckle without a grip.  It would die in a few days.

Hairless

Lions with this have a decent survival chance, but can easily get sick or killed due to the lack of fur protecting their skin. They'd probably be sunburned alot. Perhaps an item could be bought to warm up the lion, like a coat or something.

Tongueless

This would cause a lion to have no tongue. It would be an easy change to any pose, with the tongue removed if mouth is open. It would be harder to eat for these lions, and survival chances are low.

Merged hind legs

Similar to sirenomilia, the cub would not be able to use the back legs and the mutation would be fatal. This would be where the bones and skin of the hind legs merge.