I have time to elaborate on my answer.
It is my understanding that most doctors use the team approach, so if you go to Childrens Hospital of Philadelphia and see Dr. X, Dr. X will consult with the rest of the doctors on staff about your case. This is especially true in pediatrics- the community of doctors is so small they all know each other locally. So I wasn't particularly focused on finding a certain doctor as I was a hospital.
I see your son is 20. Does that put him in between adult & peds? Can you go either way? What way are you leaning?
There came a time when Eric's doctors suggested we get another opinion, they recommended either Cincinnati Childrens Hospital Bone Marrow Failure Clinic or Childrens Hospital of Philadelphia. At the time, US News ranked CHOP #1 and Cinci #2. Because Cinci was closer we went there. Now I see they're ranked #1. I don't think it matters past the top 10, I help compile the statistics where I work (a college) and I see how our rankings change yearly based on things I don't think should matter. Also, the definition of statistics is lying with numbers.
Childrens Hospitals rankings are here:
http://health.usnews.com/best-hospit...atric-rankings. I looked at the Cancer rankings because it's the disease that most closely resembles AA.
I hope this helps you.