[Allogeneic hematopoietic stem cell transplantation for aplastic anemia]

The addition of the thrombopoietin receptor agonist eltrombopag to immunosuppressive therapy (IST) with horse antithymocyte globulin and cyclosporin A has improved response to initial therapy for aplastic anemia, but about one-third of patients still require allogeneic hematopoietic stem cell transplantation (HSCT) due to resistance or relapse. Allogeneic HSCT as initial therapy is indicated when the patient is younger than 40 years of age (especially <20 years) and has an HLA-matched sibling donor. On the other hand, fulminant aplastic anemia, in which the neutrophil count is 0 even with G-CSF administration, requires transplantation regardless of donor type. When an HLA-matched donor is not available and an early transplant is needed, cord blood transplantation and haploidentical transplantation are options. In the past few years, haploidentical transplantation with post-transplantation cyclophosphamide (PTCY) as GVHD prophylaxis has been shown to produce favorable outcomes in patients with aplastic anemia. A retrospective study in Japan also showed a good engraftment rate after haploidentical transplantation with PTCY. This review discusses transplant indications for aplastic anemia and selection of donor type and conditioning regimen.