Hi!
I have AIH. I was diagnosed in January of 2007. My ANA showed up positive in 2003. I was having joint pain in my hands. So I was referred to a rheumatologist. Annually they monitored me for lupus/RA/connective tissue disorders as the only thing that came back positive was the ANA. They had run different antibody tests specific for these diseases too, all were negative. Perhaps had someone started checking my LFT's (liver function tests) sooner, something would have shown up, who knows. In retrospect, I would have asked if I had even known about autoimmune hepatitis. I was diagnosed after having a bout with nausea and vomitting followed by jaundice.
My advice to you, ask the doc to run other antibody tests for the connective tissue disorders and check LFT's. Then if something else is positive, they'll know which way to go. I was also told that sometimes people have a positive ANA and it never develops into anything else.
Good luck and take care!