SAMHD1 and Aicardi-Goutieres syndrome: Up to now, nine genes (TREX1, RNASEH2B, RNASEH2A, RNASEH2C, ADAR1, SAMHD1, IFIH1, LSM11, and RNU7-1), associated with AGS phenotype have been discovered, which are all involved in nucleic acids (NAs) metabolism or signaling (4–6).