I'm hoping this is an appropriate question for this stack group.
For several years I've been playing with a plot for a novel whose protagonist is a woman whose body does not seem to age. Science fiction, of course, but I'd like to base it on a real syndrome that I vaguely recall hearing about some years ago, and which powerfully caught my imagination.
I know that progeria (pitchforked into the public eye by Benjamin Button) is the exact opposite...children who seem to age before their time.
Is there a real life syndrome or condition which would cause a child's body to stop maturing, and to always have the appearance of a child? I just need a name, googling various combinations of keywords hasn't found me anything close.