I was just looking around at information on Geographic tounges. A lot of the sites I read say it is due to not having certain vitamins and things like that, however I too was born with Geographic tounge. I still have it after eighteen years, with no great change. It isn't bothersome at all apart from getting itchy when I eat, or more often drink, things that contain a high level of citrus. So, I think it is permanent.
I was born with it too, my father has it as well so I guess I got it from him, and me and him have had it our whole lives, but it isn't bothersome unless you eat sour foods or things that are too salty, and if the tongue does hurt or itch just try putting honey or sugar on your grandsons tongue and he will be fine
I wAs born with A geographic tounge to nd it's not a problem mine don't itch or nothing it actully feels normal well I don't know what a normal tounge feels like but it's nothing serious and at first I didn't know what It was I was the only one with my tounge like this untill d dentist told me what it was so you have nothing to worry about were just rarend I'm fifteen