Hi Jojo,
Hypocellular myelodysplasia and AA are hard to distinguish between when there is dysplasia but no cytogenetic abnormalities or increased blasts. This is because getting a sense of the "significance" of the dysplasia is difficult in a hypocellular marrow. Your son's result don't indicate dysplasia, which is good. I'm assuming that your son's underlying chromosome issue is unrelated to MDS.
With AA, kids usually have a great response to both transplants and immune suppressant therapy. However, if your son does have AA, time is of the essence, so act fast. Get your second opinion ASAP. Research on line to find a center with someone that specializes in Aplastic Anemia (which is rarer), not just MDS. Also, there are EXCELLENT webinars on AA at the Aplastic Anemia and MDS international Foundation website at:
http://live.blueskybroadcast.com/bsb...T=944&CAT=1031
Another thing that I would recommend doing is a Google search on "Aplastic Anemia" and any medications that your son may be taking.
I wish you both the best!