Our daughter has had juvenile myositis since 2002 and has been doing very well since 2005. Conventional meds (steroids and immune suppressants) are the only treatment, but some complementary therapies (fish oil, PT, etc.) might help the meds.
. They are an all volunteer nonprofit dedicated to finding a cure for JM, JDM, PM and IBM. The message board is very helpful in finding help, doctors, treatment information and so on.
Best of luck.