Hi Kelly.
I also have Jo1 antisynthetase, and I can tell you that myositis can, and generally is a big part of it. I have polymyositis. It has affected all the muscles in my body. Mine started in the hands and fingers, but was initially dismissed as part of getting older, and "maybe spending too much time on the computer". It is pretty obvious to me that with you having elevated ck levels, and the pain and weakness in your fingers that has been going away with the prednisone, that there is a very good likely-hood that you have polymyositis. both the emg and the biopsy should have very little problem showing it, even while being on prednisone. I have had the biopsy, as well as several emg's. Even after almost a year of prednisone, the emg still shows the muscle "damage"
As far as the IVIG goes, if you can get it, I would personally recommend it. It is a different type of treatment then the rituximab. Rituximab is an immunosuppressent. It is meant to lower your immune system, thus preventing it from attacking your body.
The IVIG, from what they can figure, actually attaches itself to the antibodies (in our case JO1) and renders them inneffective. I am currently on Methotrexate as my immunosuppresent, with 3 days of IVIG infussions every 3 weeks. I can tell you, even though the methotrexate really helps, I would not be walking well without the IVIG. I think you will discover that most people taking it would not be willing to stop it for anything. We use Privigen brand here in Canada, and there are very few problems. Generally the only side effect to it is when you are actually have the treatment, you can have a headache if administered to quickly. Tylenol takes care of the problem.....
I have been taking the IVIG for almost a year now, and will probably be taking it for the rest of my life. IVIG usually lasts approximately 4 weeks in the body, thus having the treatment on a regular long term basis.
Even though I am still unable to work due to my ILD, I am able to be relatively stable, and have been able to "enjoy" the summer so far. The heat really exhausts me quickly, but I try to rest lots, and carefully choose what activities to do.
Hope this helps you.
Take care and God Bless.
Wayne