TREX1 and Aicardi-Goutieres syndrome: Thus far, five genes (TREX1, RNASEH2A, RNASEH2B, RNASEH2C, and SAMHD1) have been linked to AGS and are related to an inability to remove cellular nucleotide debris intracellularly (Ali et al., 2006; Crow et al., 2006; Rice et al., 2009; Thiele et al., 2010; Xin et al., 2011).