Whereas IL-1 and IL-6 are established therapeutic targets for SD (12, 13), IL-18 and IFN-γ (also known as type II IFN) are key contributors to the pathophysiology of MAS, and high levels of these cytokines as well as their downstream products can serve as diagnostic markers of MAS (14–17). The gene discussed is IL6; the disease is macrophage activation syndrome.