will playing the guitar inevitably give me this syndrome no matter what? how fatal is it?
Well the condition is in no way fatal, but it would certainly be a pain in the ass to play with. Certain ways of holding the guitar (usually improperly) can lead to it happening.
when your hands or wrists start to hurt, take a 5 minout brake. if it persists, take a day or 2 off. let it recover fully so dont hurt yourself.
I have it, it's no biggie really. But your hand will be real bad after a long session.

A mix of anchoring, wanking and gaming got it for me.
Quote by AlanHB
Yeah well in special UG land chords = noob, scales = intermediate and modes = advanced. Most users are trying to finish the game on hard because then you get the trophies for noob and intermediate difficulties upon completion anyway.
No, it's not inevitable.

1) Stretch before playing. No exceptions. A good stretch is the one where you you grab one hand with the other and bend it backwards until you feel a stretch in your forearm, and hold for 10-15 seconds. One of the John Petrucci videos has a great section on all the stretches he does.
1a) Stretch during playing. As in take mini breaks (like 30 seconds) now and again and stretch.
2) After stretching, ease into your guitar playing with a warm up. I doesn't really matter what you do, as long as it's slow, and not difficult.
3) Take breaks. Do no more than 30-40 mins, without a 10 minute break in between. This also keeps you mentally more focused, as it's extremely hard to concentrate on something for like 4 hrs straight!
4) Focus on playing as relaxed and tension free as possible. Don't play faster than you are able to play cleanly. Not only will this help protect your joints, but it will make you a better player, as you have to kick the tension in order to play at a high level.
5) Avoid playing too much (like marathon 6 and 8 hr sessions). Unless you've got really good, relaxed technique, it's going to take a toll on your joints. Even with great technique there's going to be some fatigue. I think you can achieve just as much with 2-3 hours of really focused practice.
6) If you feel pain (not soreness, actual pain), stop immediately. All of this is just general practice tips. Go see the doctor first.