None of this necessarily has anything specific to do with musicians, but many wusicians have a lot of the predisposing factors - lots of finger motion with the hand in awkward positions, stress while doing it, tendency to practice or play for long periods without a break, tendency towards poor upper body posture. If you notice any symptoms, run, don't walk to a doctor who knows what's going on. De Quervain's tendonitis is much more common than carpal tunnel syndrome - if a doctor doesn't check for it straight off, he doesn't know enough. They should also test for diabetes and thyroid function, which are predisposing factors, and arthritis, which can have some similar symptoms. Don't allow a non-specialist to give you cortisone injections, and only then if physical therapy has failed, or if nerve conduction tests show impairment.
Early treatment is essential.
The longer you ignore it, the more it will affect the rest of your life. Some of the conditions can become permanently painful and disabling. Prevention is possible, but these days, with so many things demanding hand use, training in or at least awareness of good technique and ergonomics is a good idea. It doesn't come naturally. If I had had this book last fall, I could be playing Dufay trios this summer, instead of just starting physical therapy.