Diseases of immune dysregulation (2). Hemophagocytic lymphohistiocytosis and EBV susceptibility. Ab: antibody; AD: autosomal dominant inheritance; Ag: antigen; AIHA: autoimmune hemolytic anemia; ALPS: autoimmune lymphoproliferative syndrome; AR: autosomal recessive inheritance; Bc: B cells; CD: cluster of differentiation; CNS: central nervous system; CTL: cytotoxic T lymphocytes; def: deficiency; DNT: double-negative T cells; EBV: Epstein-Barr virus; FHL: familial hemophagocytic lymphohistiocytosis; FTT: failure to thrive; GI: gastrointestinal; GOF: gain-of-function; HLH: hemophagocytic lymphohistiocytosis; (H)SM: (hepato)splenomegaly; IBD: inflammatory bowel disease; Ig: immunoglobulin; LOF: loss-of-function; iNKT: invariant NK T cells; NK: natural killer cells; Nl: normal; RTE: recent thymic emigrant; sd: syndrome; Tc: T cells; Treg: regulatory T cells; VZV: varicella zona virus; WBC: white blood cells; XL: X-linked inheritance. A searchable PDF file containing all figures in this article can be found under the “Supplements” tab.