You wrote: "My sister was diagnosed with MS (relapsing remitting) 9 years ago. Her conditon started getting noticeably worse about 5 years ago. She has tried Avonex, betaferon and copaxone but cannot tolerate any of these drugs. She has recently started taking Azathioprine, but this isn't having any effect very quickly. Her main symptons are extreme fatigue and pain, mostly down one side. She also has problems with balance and stability, and short term memory loss which may be due to the pain killers (codeine and opiates)."
Multiple sclerosis is an autoimmune disease. During autoimmune diseases, the immune system attacks some of the body's own structures causing inflammation. In case of multiple sclerosis, the immune system attacks the myelin coverings of the nerves and nerve tracts. During MS, as in all autoimmune diseases, the provoker is not known and there exists no etiological therapy. There is only a therapy that will suppress the immune process and calm inflammation. Immuno-suppressive therapy is not specific for any autoimmune disease. In other words, the same immunosuppressive drugs are used for many autoimmune diseases. Corticosteroids and chemotherapeutic drugs are the most common immuno-suppressive drugs used for treatment of these conditions. The prognosis of MS is variable and unfortunately progressive even with therapy. You can consult a neurologist for an expert opinion.