How To Control Wbc Levels In Patients With Polymyositis?

I am 42 years old ( male), suffering from polymyositis since 15 years ago, the level of CPK start to increase to very high level before two monthes and was (10000), I took pridnosolone 200 mg per day ( tablets) for 5 days after then I took pridnosolone 40mg ( 8 tablet of 5mg per day ) for month,and cellcept 500 (two tablets twice in a day, 2x2 ) for 7 days only , I tested the CPK and it was 580, but the test of WBC level was high , is 14200.I reduced the pridnoselone to 35mg ( 7 tablets of 5mg per day), what is the procedure ,should I follow to reduce the WBC level?Should I taking cellcept for another course?what is the preferd treatment instead of pridnosolone if its available?