I never take a week completely off from the gym but if I am feeling burnt out, I'll do a de-load week.
It's really up to you. You won't loose any muscle during a week off from the gym but you might gain some weight if you aren't active in other ways. That's the biggest problem I see people get into when they take a week off from the gym. They take it completely off of all exercise and then gain a bunch of weight.
During your week off from the gym, I would purse other forms of activity like yoga, swimming etc.