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]. The gene discussed is CXCL9; the disease is Cowden syndrome 1.