So, in the Shadowrun world, elfs and dwarfs are born that way, forming as their metatype in the womb. Orks and trolls, OTOH, form as a human and then suddenly change into their metatype at puberty, unless their parents were already Goblinized in which case they are born as the metatype of the parents. My question is, then, does it happen anywhere in the fluff that a person can be born to human parents but be born an ork (troll might be kinda hard) or that a human can "Goblinize" into a dwarf or an elf? I have seen a few characters who change into elves run in people's home games, but I don't think the fluff ever says that such is possible. But I have not read all of the novels and sourcebooks yet.
Does anyone know of a case of this unusual occurrence happening in official Shadowrun? Is it a possible concept in standard Shadowrun? Or is it doomed to always be a house rule "whatever works for you" thing relegated to some people's groups?