Hemophagocytosis after bone marrow transplantation for JAK3-deficient severe combined immunodeficiency.

HSCT is the optimal treatment for patients with SCID. In particular, HSCT from a HLA-identical donor gives rise to successful engraftment with long survival. We report a six-month-old girl with JAK3-deficient SCID who developed hemophagocytosis after BMT without conditioning from her HLA-identical father. She had suffered from pneumonia and hepatitis before BMT. Prophylaxis for GVHD was short-term methotrexate and tacrolimus. On day 18 after BMT, the patient developed hemophagocytosis in bone marrow when donor lymphocytes were increasing in peripheral blood. Analysis of chimerism confirmed host origin of macrophages and donor origin of lymphocytes. Thus, host macrophage activation was presumably induced in response to donor lymphocytes through immunoreaction to infections and/or alloantigens. HSCT for SCID necessitates caution with respect to hemophagocytosis.