Unlike in Aicardi–Goutières syndrome, where mutations in the catalytic domain of TREX1 lead to a loss of enzymatic activity, TREX1 mutations in RVCL-S are found in the C-terminal domain that links TREX1 to the endoplasmatic reticulum [5, 20]. This evidence concerns the gene TREX1 and Aicardi-Goutières syndrome.