SAMHD1 and Aicardi-Goutieres syndrome: Other enzymes involved in nucleic acid metabolism have also been found to be mutated in AGS patients, including: the 3′ to 5′ single‐stranded DNA exonuclease TREX1 (Crow et al, 2006), the 3′ to 5′ exonuclease and dNTP hydrolase SAMHD1 (Rice et al, 2009), the RNA adenosine deaminase ADAR1 (Rice et al, 2012), and the cytosolic double‐stranded RNA receptor gene IFIH1 (Rice et al, 2014).