If you have ever seen Unbreakable,
Samuel L Jackson's character has a kind of reverse super power: he is incredibly susceptible to injury and illness. Everyday activities could kill him. There is no upside to having very brittle bones.
Is there anything like this in the X Men?
Another example of what I am looking for would be Christopher Snow in Dean Koontz's
This character could not go out in the sun, he burned easily, his skin could not ever repair the damage and eventually he was sure he would die from skin cancer young. There were no benefits to this (like in a vampire where there are trade offs). His illness was ONLY a hindrance.