同系骨髄移植が著効した最重症再生不良性貧血の１例

Aplastic anemia is a bone marrow failure caused by severely curtailed hematopoietic stem cells （HSCs） and dysregulation of ambient immune cells. Immumo-suppressive conditioning followed by allogeneic HSC transplantation is currently a mainstay in treatment for patients at a younger age or those refractory to conventional immunosuppressive remedies. Syngeneic HSC transplantation appears to be promising, but has been very rarely performed ; therefore, its impact on a long-term outcome as well as the best preparative measures for HSC engraftment and immune amelioration are still largely unknown. Here, we reported a successful and beneficial syngeneic HSC transplantation for a refractory case with very severe aplastic anemia. A 30-year-old female presented high fever after tooth extraction, and was diagnosed with very severe aplastic anemia. Cyclosporine and anti-thymocyte globulin were initiated, but showed no hematological effects. After obtaining an informed consent, she underwent bone marrow transplantation from a genetically identical twin following an non-myeloablative conditioning regimen consisted of cyclophosphamide （750mg/m２, 4 days）, fludarabine phosphate （25mg/m２, 4 days）. Cyclosporine was given for acute GvHD prophylaxis. Her neutrophils recovered over 500/μl on 12 days after the transplantation, and her blood counts have been maintained in a normal range over 7 years thereafter. Although a fate of HSCs from a genetically identical twin and an immune response of ambient cells in the bone marrow in recipients remains largely unknown, from the present case and previously reported cases, we dare to recommend immunoablative conditioning and acute GvHD prophylaxis in syngeneic HSC transplantation for a refractory case with aplastic anemia for better engraftment and sustained onward recovery of hematopoiesis.