Chronic active Epstein–Barr virus infection with mosquito allergy successfully treated with reduced‐intensity unrelated allogeneic bone marrow transplantation in a boy

: EBV‐infected T‐/NK cells play an important role in the pathogenesis of mosquito allergy, and the prognosis of most patients with mosquito allergy is poor without proper treatment. We describe a 13‐yr‐old boy who had CAEBV with mosquito allergy and was successfully treated with BMT from an unrelated donor after reduced‐intensity preconditioning. Because combination chemotherapy failed to achieve CR, we performed unrelated BMT to reconstitute normal immunity and eradicate any residual EBV‐infected cells. To reduce complications after BMT, we selected a reduced‐intensity preconditioning regimen consisting of fludarabine, l‐phenylalanine mustard, and antithymocyte Ig instead of a conventional myeloablative preconditioning. Although grade II acute GVHD developed, it was successfully controlled with immunosuppressive therapy. After 27 months, the patient has been well without any signs of CAEBV, and the EBV DNA has been undetectable with real‐time PCR analysis. We conclude that RIST from the bone marrow of an unrelated donor is indicated for some patients who have CAEBV that is refractory to chemotherapy and who have no HLA‐matched related donors or cord blood as a source of stem cells.