SAMHD1 and Aicardi-Goutieres syndrome: Aicardi-Goutières Syndrome (AGS), the prototype of the type I interferonopathies, is a genetically determined encephalopathy caused by mutations in any one of ten distinct genes (ADAR, IFIH1, RNASEH2A, RNASEH2B, RNASEH2C, SAMHD1, TREX1, DNASE2, LSM11 and RNU7-1) [1, 2].