I’m not new to Lioden but it’s been years since I’ve been properly active and I’m aiming to jump back in again. I took a quick look through the pinned post about proposed mutations and didn’t see this included, if I missed it feel free to let me know and I apologize for the redundancy.

Congenital Erythropoietic Porphyria is a condition present at birth which causes blueish gums and brown teeth which fluoresce when exposed to UV light.

The simplest way to implement this would be to just recolor the gums + teeth in poses where they’re visible. For optional added flare they can appear red at night and brown during the day, which I know isn’t the same as UV light but I think close enough for aesthetic purposes.

It’s a recessive condition so can work as an inherited mutation or as a spontaneous mutation depending on what the staff would prefer.

The main quality of life complication is photosensitivity, so if the staff wanted to include that in a similar way to blind, etc mechanics that’s an option but I don’t think strictly necessary. I think for the purposes of the game porphyria would work just as well as a simple cosmetic mutation.

Another article on the condition in cats.