One of my LGDs, Kody, had a similar spot, in almost the same location, last month. One day it just looked like he had sat in some mud or something--just a round, dark, slightly wet-looking patch. The next day the hair was all gone and looked just like that. I keep plenty of antibiotics on hand, so just put him on Cephalexin. It would look like it had cleared, but then another little spot would show up on the edge of the main patch. It took probably 3 weeks for the whole thing to finally clear up, but it is fine now and there is nice smooth hair grown in. I think Kody's was caused initially by the horrible bout of fleas we had here. Usually Frontline works well, but it did nothing this year. Had to switch to Comfortis. Anyway, it should clear up just fine.