I sympathize with your decision struggles and send my best wishes to you and your family. My starting point was quite similar so I thought I would share some details. Please know though I'm not trying to sway you one way or another, every person and transplant is different.
I received a Reduced Intensity Bone Marrow Transplant Jan. 31, 2013, from a 9/10 matched unrelated donor. I was 30 (now 31). I was diagnosed with PNH and Moderate to Severe AA in Nov. 2011. I had an ATG in Feb. 2012 that was unsuccessful. My PNH was rather pronounced with 89 percent of my cells presenting as PNH cells.
The US standard for matching uses 10 HLA markers, of which a subcategory 8 are the most important. A study was published (I can't find it right now) in Europe, within the last few years, that only used those 8 markers. I believe 8 is the standard in Europe? My donor and I had those dominant 8 matched.
My doctor requested Bone Marrow over Stem Cells, as those patients tend to have less GVHD (as mentioned by someone else, AA/PNH patients do NOT benefit from GVHD). Statistically, cells from young adult, male donors have better success rates (mine happened to be).
It's easy to get lost in the statistics and the stories. I went through the same as everyone else, and read everything I could before deciding if I should proceed with a transplant. Patient blogs, medical journals, articles, etc... What I learned though was that it truly is different for each person. I read descriptions about many successful at-risk patients, and tragedies about "ideal" patients with donors that were from twins.
My doctor and I discussed the haplotransplant at Johns Hopkins as an option, but felt my donor was a strong enough match (in-part, because of that study). And since it is good practice and those around me felt it was important, I had a second opinion from a different facility and they agreed.
I've heard great things about the haplos and it has opened many doors not only for people, but new technology. One day they no doubt will be doing half-matched unrelated donors. Currently it's new and could be considered more of a risk.
I've been supremely lucky and have experienced zero GVHD so far (let's hope that continues!). And few other complications. Before a transplant they do a lot of testing to determine if one is medically able to have the transplant and how to gage one's viability. I had a low pulmonary function test (due to my PNH) and very high liver enzymes (due to medications, the night before my scheduled transplant, I spiked a fever and it was pushed back a month). I had some complications along the way, nothing compared to what I've read on here though.
I had an unnamed virus attack in June, it caused some temporary chaos, a stint back in my old transplant room, but I slowly recovered from that.
My numbers are currently stable, my pulmonary function is slowly recovering (it's checked every three months), and I'm about to start phlebotomy to remove excess Iron due to the multitude of RBC transfusions (a common problem and treatment for people with these diseases). I'm back to work and while it's a struggle at times, I continue to improve.
I'm still on my immunosuppressants and will begin to taper at my one year mark. My doctor said that will be a test, sometimes GVHD does not appear until the medication is tapered.
For your question about GVHD timing. Technically it can show up at any time, but the further from transplant the least likely it is to occur and tends to be less severe. If it does happen, it can go away in months to years, or last forever. It really is that variable.
I agree with the others, it's important to really trust your medical team and feel you have a good connection with them. The hematologist should be a PNH and Aplastic Anemia specialist. Aplastic Anemia and PNH is different from cancer and the treatment details are different.
While considering where to have the transplant (if not having the haplo) it may be helpful to keep in mind that after the in-patient time, facilitates typically require patients to stay within a certain mile range for an extended period of time post-transplant. Each facility has different standards and it depends on the health of the patient.
Variable answers and data: Yea, different doctors and facilities follow different practices. Some doctors are more conservative than others. Studies are different depending on when they were done, what treatment was used, etc… It's a lot to sift through.
Below is a study published in Blood Journal about Long-term outcomes for AA patients. Once again though, the statistics really do not capture the details of individuals and the many success stories there really are.
http://bloodjournal.hematologylibrar...03/7/2490.long
I hope the best for your son. Please feel free to send me a message if you have any questions.