In a case-control study of AGS, a phenotypically similar inflammatory disorder caused by mutations in any of six IFN-stimulating genes (SAMHD1, TREX1, RNASEH2A, RNASEH2B, RNASEH2C and ADAR), 90% (74/82) of affected patients vs. 7% (2/29) of controls had a positive IFN score, reflecting increased expression of these genes [3]. The gene discussed is SAMHD1; the disease is Aicardi-Goutieres syndrome.