acne and tapering off prednisone

My son has been on 60 mg. daily of accutane for about 3 months.  He is tapering off prednisone (started at 70 mg, now down to 5 mg. daily).  He has acne conglobata, very severe on his back, chest.  Most of the acne had calmed down, however now his face is beginning to break out again and some on his back.  I will tell you that his back from his shoulders down his trunk was very severe, bleeding very painful.  Not as bad on his chest, but still inflamed and broken out.  My question is should he be breaking out in this third month on the accutane or is it being caused by coming off the prednisone?