In patients with MAS, free IL-18 concentrations significantly correlated with the clinical status and the biologic markers of MAS such as anemia (p < 0.001), hyper-triglyceridemia, and hyper-ferritinemia and also with markers of Th1 lymphocyte and macrophage activation, such as the elevated concentrations of IFNγ and of soluble IL-2 receptor and of the concentrations of the TNFα receptor (15). The gene discussed is IFNG; the disease is macrophage activation syndrome.