Circulating blood levels of IL-18 are consistently higher in patients with AOSD or SJIA with active MAS than those without MAS or in other inflammatory rheumatic diseases without cytokine storm, such as rheumatoid arthritis and systemic lupus erythematous [63–65], suggesting that IL-18 may drive a cytokine storm rather than just rheumatic inflammation. The gene discussed is IL18; the disease is macrophage activation syndrome.