marfan syndrome would be an interesting mutation to add but would require some new lineart and
decor redraws

appears: at birth
lethal: possibly, between 3-15 years
gameplay affect: low chance of catching prey

affects: the lion may have a lowered chance at catching prey on hunts due to blurry vision and fatigue. they can still be bred; the mutation has a 9% chance of being passed on to cubs. there'd be the possibility of the lion's lung collapsing, resulting in death between the ages of 3-15 years (player would get a notice when this happens).

month 0 notice
"your lioness notices something off about one of her cubs. its body is long and narrow, with long paws! she feels like something's up, but the cub just suckles milk like all the others."

month 1 notice
"looks like cub is playing like all the others... its mother doesn't let her guard down, but everything seems okay."

month 2 notice
"cub's mother can finally relax when it walks by. hopefully, cub's health will remain this good throughout its life."

death/collapsed lung notice
"the whole pride was woken up last night to find cub coughing and wheezing. it gasped for air and, despite your best attempts to help it breathe, cub passed away due to a collapsed lung."