Sorry to hear about this. Just a thought...might it be that when your child was initially diagnosed with ITP, he was in an early stage of either AA and therefore inconclusive diagnosis?
Has your son had nosebleeds or bleeding from the gums? The only other thing besides the bruises and petichae that sounds familiar to me, is the shortness of breath. I recall my then 10 y-o son saying, "My heart is beating really fast and I can feel it." Might this be the chest pain your son is experiencing?
With your child's low platelet count, I would be concerned about possible internal bleeding. Please ask his doctor what she recommends as far as activity to eliminate or avoid. I'm wondering if his body aches/pains are related to this.
Just a couple of things that come to mind that you might want to ask his doctor about.
I hope tomorrow's BM Biopsy will give you a definite answer as to what is going on and how to best treat your child.
06/2004 my son was dx with SAA at the age of 10. No sibling BM match. He underwent ATG (H)/CsA. Relapsed 05/12 & dx'ed w/PNH. Currently in wait/see mode for Solaris as he is asymptomatic...