NK-cell post-transplant lymphoproliferative disease with chronic active Epstein–Barr virus infection-like clinical findings.

• A rare Epstein–Barr virus-associated post-transplant lymphoproliferative disease. • Flow cytometric in situ hybridization was useful for detecting the infected cells. • Further research is needed to establish appropriate treatment strategies. A 69-year-old man who underwent cord blood transplantation seven years ago was admitted because of fever, elevated liver enzymes and thrombocytopenia. Bone marrow aspirate revealed hemophagocytic lymphohistiocytosis. Viral capsid antigen (VCA)-immunoglobulin (Ig) G, VCA-IgM, VCA-IgA, Epstein–Barr virus nuclear antigen-IgG, early antigen-diffuse-type and restricted-type (EA-DR) IgG, and EA-DR IgA titers were 2560, <10, 10, 40, 40, and <10, respectively. Real-time polymerase chain reaction assay of peripheral whole blood for Epstein–Barr virus-deoxyribonucleic acid (EBV-DNA) revealed 240,000 copies/μg DNA. Flow cytometric in situ hybridization assay confirmed that EBV-infected cells were NK-cells. Clonality evaluation by Southern blot assay of EBV-DNA terminal repeats proved to be bi-clonal. Accordingly, we made a diagnosis of NK-cell post-transplant lymphoproliferative disease with chronic active EBV infection-like clinical findings (CAEBV-like NK-cell PTLD). Although CAEBV-like PTLD is extremely rare, its prognosis seems to be very poor. The disease should be considered in such patients who present persistent or recurrent infectious mononucleosis-like symptoms after transplantation. [ABSTRACT FROM AUTHOR]