It's definitely possible that a disability is creating the extreme score disparity. There are lots of resources available on twice exceptional students. Check out the 2E newsletter at http://www.2enewsletter.com/welcome%20page.htm or the Twice Exceptional network of the National Association for Gifted Students at http://www.nagc.org/index.aspx?id=973 for more information, once you get your full subtest results!