Successful treatment with allogenic hematopoietic stem cell transplantation of a severe congenital neutropenia patient harboring a novel ELANE mutation.

We report a 4-year-old boy with severe congenital neutropenia (SCN), who was successfully treated with hematopoietic stem cell transplantation (HSCT). The patient had frequently developed bacterial infections since 6 months of age, and showed severe neutropenia below 100/µl at 1 year and 4 months of age. The patient harbored a heterozygous missense mutation in ELANE exon 3 (p.Q73P, g.2253 A>C). This was a novel de novo mutation, and he was thus diagnosed as having SCN. Because of failure to respond to granulocyte colony-stimulating factor treatment and repeated admissions due to bacterial infections, allogeneic HSCT was performed from a serologically matched unrelated donor following the conditioning regimen: fludarabine/melphalan/anti-thymocyte globulin and a low dose of total body irradiation. Tacrolimus and a short course of methotrexate were used for graft-versus-host disease prophylaxis. Engraftment was achieved at day 12, and the patient maintained normal hematopoiesis for over 15 months after HSCT. We concluded that HSCT is a useful treatment for SCN patients, especially those who are at high risk for leukemic transformation. However, a larger number of SCN patients and longer follow-up are necessary to identify appropriate conditioning regimens and long-term prognosis.