TREX1 and Aicardi-Goutières syndrome: TREX1 acts as a negative regulator of the type I interferon response through degradation of intracellular endogenous nucleic acids.4 Bi-allelic mutations in TREX1 cause the type I interferonopathy Aicardi–Goutières syndrome (AGS), leading many to speculate that RVCL-S might also be an interferon-associated disease.