[HLA-haploidentical allogeneic hematopoietic stem cell transplantation using FluMelTBI conditioning for an elderly patient with fulminant aplastic anemia during treatment for chronic lymphocytic leukemia].

A 66-year-old woman was diagnosed with chronic lymphocytic leukemia (CLL) due to the finding of leukocytosis and started acalabrutinib and obinutuzumab (AO) therapy. After three cycles of AO therapy, she developed severe pancytopenia with hypoplastic bone marrow and was diagnosed with fulminant aplastic anemia (AA) due to neutropenia with no response to granulocyte colony-stimulating factor. One month after the onset of AA, she received HLA-haploidentical allogeneic hematopoietic stem cell transplantation (haplo-SCT) from a daughter using FluMelTBI (fludarabine 180 mg/m2, melphalan 80 mg/m2, total body irradiation 4 Gy) as the conditioning regimen and tacrolimus, mycophenolate mofetil, and post-transplant cyclophosphamide (PTCy) for graft-versus-host disease (GVHD) prophylaxis. Rapid engraftment was achieved without GVHD or any other serious complications, and CLL has remained in remission. Haplo-SCT using PTCy is considered to be a useful emergency transplantation option for elderly patients with fulminant AA, and more cases are needed to evaluate its safety and efficacy.