Stacy, that happened to my Specks a couple of years ago (she's a 100% indoor kitty) and it turned out to be an allergy to flees. I must have brought them into the house. A dose of Advantage and they were gone and the fur all grew back.

You may want to get yourself a flea comb and comb down by the base of the tail. If you see any tiny black specs, that could be "flee dirt" or "flee poo." Have a glass of water handy and if you see any flees, then drown them. It's really the only way of killing them.

Good luck, and keep us posted.