Mutations in nine genes, namely, TREX1 (AGS1), RNASEH2A (AGS2), RNASEH2B (AGS3), RNASEH2C (AGS4), SAMHD1 (AGS5), ADAR1 (AGS6), IFIH1 (AGS7), LSM11, and RNU7-1, have been identified as the causative agent of AGS (4, 11). The gene discussed is SAMHD1; the disease is Aicardi-Goutieres syndrome.