In the manga (and now Netflix anime) "Dorohedoro", Professor Kasukabe looks remarkably young for his profession.

It turns out that a sorcerer de-aged him to young teen-looking as "practice." (In this story, sorcerers use ordinary humans as experimental subjects to get better at magic.) He hasn't aged in the decade plus since that attack.

Since Kasukabe lives in a crapsack world where teenagers have no less (or more) rights than adults, it hasn't really held him back, it just startles people when they realize he's a mad scientist of renown and not some random kid.