I have heard of one case in particular where a young woman's anorexia was apparently triggered by Lyme disease. She couldn't make headway in treating the anorexia until she had successfully treated the Lyme.
Lyme and its co-infections can cause a wide array of troubling symptoms, including both gastrointestinal problems and psychiatric issues, both of which might be involved with anorexia.
If you have reason to suspect you have Lyme, it's essential to find a doctor with experience treating its many manifestations. You might google "Robert Bransfield" and "lyme." He's worked extensively with the psychiatric manifestations of Lyme disease and co-infections (other nasty infections carried by the same ticks that carry Lyme.)
Good sources of info about Lyme disease:
http://www.canlyme.com
http://www.lymenet.org
http://www.lymeinfo.net
http://www.lymediseaseassociation.org
http://www.ilads.org
http://www.betterhealthguy.com
http://www.publichealthalert.com
http://www.freewebs.com/teenswithlyme
http://www.lymetimes.org

not usually.

no. a huge red rash in a circular shape with a white center is the biggest clue.