IL18 and macrophage activation syndrome: Alternatively, when the CS is caused by macrophage activation syndrome (MAF), the serum levels of interleukin 18 are elevated, while CS due to HLH is often characterized by elevated levels of TNF-a, interferon γ (IFN-γ), interleukin 1 (IL-1), IL-4, IL-6, IL-8, IL-10, IL-18, CXCL9, and CXCL10 [1].