I don't like the term "disease" because people seem to be of the opinion that diseases are contagious, or that it is curable, or just even because I don't ever want to have anyone think my daughter is "diseased" and so they think they need to avoid her for fear they could get it.  I also don't like the term "disorder," because that sounds too much like inferring that my daughter is "less than perfect", it sounds too negative to me.  So I always say "medical condition," it sounds neutral to me, whereas disease and disorder both sound too negative.