HMGB1 and macrophage activation syndrome: IL-1 and IL-18 are well-established and important mediators in MAS-HLH (Crayne et al. 2019; Ravelli et al. 2012; Schulert and Canna 2018; Weiss et al. 2018), while the presence and a functional role of HMGB1 in these conditions remain to be studied.