Keywords: ATG; Antithymocyte globulin; CTL; Cytotoxic T lymphocyte; EBV; Epstein-Barr virus; FHLH; Familial hemophagocytic lymphohistiocytosis; HCT; HLH; Hematopoietic stem cell transplantation; Hemophagocytic lymphohistiocytosis; IFN; IL; Interferon; Interleukin; MAC; MAS; Macrophage activation syndrome; Myeloablative conditioning; NK; Natural killer; RIC; Reduced-intensity conditioning; X-linked inhibitor of apoptosis; X-linked lymphoproliferative disease; XIAP; XLP.