TREX1 and Aicardi-Goutieres syndrome: In Aicardi-Goutières syndrome (AGS), which represents a rare monogenic variant of the prototypic autoimmune disease systemic lupus erythematosus, defects of either TREX1 [2], RNaseH2 (subunits A, B and C) [3], ADAR1 [4], MDA5 (Ifih1) [5], or SAMHD1 cause the cell to spontaneously produce large amounts of type I IFN [6].