SAMHD1 and Aicardi-Goutieres syndrome: Many genes mutated in AGS, such as SAMHD1, RNase H2, and Trex1, are involved in various cellular nucleic acid metabolisms, suggesting that the interrupted nucleic acid metabolisms may trigger cellular nucleic acid immune sensing, which potentially induces the activation of the cellular innate immune responses without any infection events (3, 4, 5).