Mouse models of MAS/HLH also present with increased levels of IL-18 (Weiss et al., 2018; Girard-Guyonvarc'h et al., 2018) and development of MAS is worse in IL-18BP knockout mice (Girard-Guyonvarc'h et al., 2018). The gene discussed is IL18; the disease is macrophage activation syndrome.