USP18 and Aicardi-Goutières syndrome: We next examined baseline gene expression (qPCR) of archetypal interferon stimulated genes (ISGs) IFI27, USP18, MX1, OASL, IRF7, and MX2, and those ISGs found highly expressed in PBMCs from the type 1 interferonopathy, Aicardi-Goutières syndrome (AGS) patients (IFI27, ISG15, IFI44L, and RSAD2) (27).