RNASEH2B and Aicardi-Goutieres syndrome: Both P1 and P2 demonstrated a mildly elevated ISG score (respectively 3.86 and 3.94) in contrast with a control group of three AGS patients with biallelic mutations in SAMHD1 (7.94), RNASEH2B (10.14), or TREX1 (11.60) (Fig. 3b, Table S5, case descriptions in supplemental data S1).