IL1B and macrophage activation syndrome: Interleukin (IL)-1 and IL-18 play a pivotal role in the pathogenesis of sJIA and AOSD.1 This is substantiated by the upregulation of IL-1α and IL-1β in healthy peripheral blood mononuclear cells24 and by improved AOSD outcomes after IL-1 inhibition.25 In addition, significant increases in serum levels of IL-18 and other cytokines have been observed in MAS.26,27 Similarly, it has been observed that although other cytokines normalise during remission, IL-18 remains elevated in inactive AOSD and sJIA.28