THE REAL DEAL.
Werewolves, by scientists and smart people, are called Lycans. Lycans Age like normal people, and can be born with it like you said. They have three forms, wolf, lycan, and human. The lycan form is what you think when you think werewolf. Wolf form is like, a normal wolf. (If you don't know human, gtfo and take your failiure with you.)
THEY ARE NOT IMMORTAL. THEY DIE BY NORMAL MEANS. DON'T BE NOOBS PL0X.
That's it, lol. x]