Pit bulls are notorious for demdodex mange. This mange is not itchy...or cause skin marks..the mange burrows in the hair follicles and just causes patches of hair loss.
I would consider getting a skin scrape...if it is only in one location, there are topicals that can help.
The other thing I think of is sometimes bacteria can cause areas of patchy moth eaten apperance, but there is usually more than one.
Have you tried any topicals on it yet?
Dr.V
Dr. D.A. Vamvakias
Veterinarian