Hello,
I was the same age as your son (17) when I was first diagnosed in July 2012 (my thread here
pdsa.org/forum-sp-534/5-newly-diagnosed-a-frequently-asked-questions/26190-newly-diagnosed-extremely-depressed.html#26190) and I was starting University. They gave me steriods which I didn't respond to and IVIg - which is only a temporary fix. The doctor recommended a spleenectomy, which I have chosen not to do after finding out it was only a 70 percent success rate. After months of falling into a hole of depression, in January; I decided to read up a lot on ITP and what I could do. I started following holistic natural treatments - calling a naturopath in my area, who ensured me that there was a big possibility that I could fall into remission. Now I personally chose this direction, I am a huge skeptic and am very cautious but started believing through naturopaths because of a family friend who is now in remission from Chrohn's disease. Naturopaths don't give you magical herbs of some sort, they find out what your son lacks in nutrition and build his immune system up from the crapper basically. I used to eat processed foods ALL the time prior to getting ITP - now scientists have found that autoimmune diseases do come from that. Naturopaths also find your food intolerances (i never knew i had wheat,dairy,corn, and nuts as an intolerance), and just clean your body and let it heal by itself.
Right before I started this, I had to unfortunately resort to Rituxan because of Doctor's pressure and the fact that my platelets were dropping like flies, that didn't help either. After the naturopathic diet starting in january till now, I have had 3 rounds of IVIg treatments when my platelets were low but have seen a huge improvement platelet wise. No I am not in remission, with Naturopaths it takes time it's not an immediate effect but I am feeling much better. My doctor appointments used to be a weekly basis and now are every 3 weeks, yes it doesn't seem much but really it's only getting better from here. Last week I was supposed to recieve IVIg once again, because it's been a while since my last check up and it was OBVIOUS that I was gonna get it, to my surprise my platelets were above the danger zone and I did not need IVIg treatment

, so i'm free for another 3 weeks till the next check up.
I would suggest you go through a naturopath because I personally believe you need to take measures to heal yourself, the harsh medicine they will give your son will only make his son worse.
ALSO he is going to have an extremely tough year, because I did. I had to start university in a different country, I had no friends, really it was the tip of the iceberg of how much it sucked. You need to help him from falling into a hole of depression and let him really focus on his studies. Don't let ITP take over your son's life. I really hope your son and I find remission soon, I will be turning 19 in October.