Hey Erin,
I'm no brainiac either, but I often wonder about this too- why IViG works well for some, and plasma works well for others...I guess that's why my neurologist wanted me to be part of that study which measures exactly that...I had to pull out of it due to my job (which I ended up quitting anyway due to the MG

)...
I know that plasma exchange definately works better for me, but I also feel drained afterwards...I look pasty for at least a week after having it done...The IViG just makes me feel weird...I literally feel like I'm full of fluid (prolly 'cause I am)...I think that I have a lot of trepidation about it too because I always have the prospect of Mad cows disease sitting in the back of my mind, even though the chances of getting it are very low...
Maybe it has to do with what antibodies are at work...I'm convinced that there are more involved than just anti-achr and anti-musk, which I think the doctors know too (seronegative MGers)...Also, a lot of MGers are prone to infections, and you gotta wonder about that...Maybe those people have MG because of molecular mimickry...I figure, if you've got an infection, those autoantibodies are going to be switched on again, because they're already 'programmed' to fight your parts, and are circulating around...If you get rid of the infection, maybe they'll be turned off...Maybe you're immunoglobulin deficient, and you're getting back what you need, fighting the infection, and thus turning off your autoantibodies too...I saw a program about a boy who had common immune deficiency disorder, and his family would notice how healthy he looked after having IViG....He also would feel fantastic after having it done...
As for the Fibro...I'm sorry that you're going through this too now...One thing that seems to be a common theme with people who have this is vitamin D deficiency, like what Annie said...I'm actually a part of another support group for this as my doc. thought that I might have had this at one point...All of the threads are, "Are you vitamin D deficient? I am!" something along those lines...There also seems to be problem with the adrenal glands and pituitary gland with people who have this...So the prednisone, at least for you, might be a big culprit...I've been having a lot of crackling, back pain, brain fog lately too...I hope that my doc. decides to lower my prednisone big time...Otherwise, there should be a new medical specialty; prednisologist
Nicky