My son is 30mo old 39lbs and 39in and for the last 1.5 years he has had an elevated CK that has been taken every six months: oldest to most recent-598, 525, 375, 301. He jumps, runs, plays, and dances.  At 1.5 he had an EMG and Nerve test, both were normal.  All other blood counts are normal and no genetic history.  Older and younger son are normal CK ranges.  How reliable is an EMG at 1.5.  Are there any posible explainations why CK comes down every six months or tests?  Thank you