One clinical example is haemophagocytic lymphohistiocytosis (HLH), a rare clinical syndrome of excessive immune activation, characterized by signs and symptoms of extreme inflammation, driven mainly by IFN‐γ and other proinflammatory cytokines with good response to emapalumab (Lounder, Bin, de Min, & Jordan, 2019; Vallurupalli & Berliner, 2019), a human monoclonal antibody to IFN‐γ. The gene discussed is IFNG; the disease is hemophagocytic syndrome.