What are the different types of bone marrow transplants, and how is a donor selected?

What are the different types of bone marrow transplants, and how is a donor selected?
What are the different types of graft versus host disease?
How do doctors decide if a child with AML needs a bone marrow transplant?
What is graft versus host disease, and why does it occur in patients with acute myeloid leukemia?
What should patients know when they are first diagnosed with BPDCN?