[Alemtuzumab-based HLA-haploidentical transplantation for relapsed/refractory aggressive NK-cell leukemia].

A 30-year-old man presented with fever of unknown origin, pancytopenia, and hepatosplenomegaly. Peripheral blood analysis revealed elevated Epstein-Barr virus (EBV) DNA levels, with EBV detected in the NK cell fraction, leading to a diagnosis of chronic active EBV disease (CAEBV). Despite immunosuppressive and etoposide therapy, fever and organ dysfunction worsened. He subsequently underwent peripheral blood stem cell transplantation (PBSCT) from an HLA-haploidentical donor with post-transplant cyclophosphamide. On day86 post-transplant, the patient developed fever, recurrent pancytopenia, elevated peripheral blood EBV-DNA levels, and abnormal lymphocytes in both peripheral blood and bone marrow, leading to a revised diagnosis of relapsed/refractory aggressive NK-cell leukemia (ANKL). The patient underwent a second haploidentical PBSCT with alemtuzumab and achieved remission for 264 days before dying of Fusarium-related infective endocarditis. Alemtuzumab, an anti-CD52 antibody, is approved for GVHD prophylaxis in allogeneic hematopoietic stem cell transplantation and may also offer antitumor effects against ANKL.