I thought this interview with De Meirlier and Hyde was interesting, especially De M's comments about a majority of patients having food intolerance or digestion issues (either months previous to a "sudden" onset or during illness), his impression that there's no 'one cause', and in particular his comment about subgroups (at 7:30 into the interview):
"How many different subgroups do you think would exist within the ME/CFS patients?"
"As many as there are patients."
http://www.youtube.com/watch?v=JWHWf1yJRac&feature=related
"How many different subgroups do you think would exist within the ME/CFS patients?"
"As many as there are patients."
http://www.youtube.com/watch?v=JWHWf1yJRac&feature=related