Girl who does not age
Aka inverted Mr. Immortal mutant power?
http://abcnews.go.com/2020/Health/Story?id=7880954&page=1
sign of first 'marvel' related mutation? This could be some defective mutant gene activated, early in stages, that was meant to prolong age such as Wolverine, but it's in the early stages and the mutation stays at a toddler stage too long.