In patients with MAS, free IL-18 but not IL-12 concentrations significantly correlated with clinical status and the biologic markers of MAS such as anemia (p < 0.001), hypertriglyceridemia, and hyperferritinemia (p < 0.01) and also with markers of Th1 lymphocyte or macrophage activation, such as elevated concentrations of IFNγ and soluble IL-2 and TNFα receptor concentrations (32). This evidence concerns the gene IL18 and macrophage activation syndrome.