Abnormal cytosolic DNA accumulation associated with TREX1 mutations is thought to lead to autoimmune diseases characterized by excessive type I interferon (IFN) and cytokine production, such as Aicardi-Goutières syndrome (AGS), which results in neuronal disorders and death in childhood (3, 9, –, 13). Here, TREX1 is linked to Aicardi-Goutieres syndrome.