TREX1 and Aicardi-Goutieres syndrome: Although a pattern of early frontal and temporal lobe swelling giving way to severe frontal and temporal lobe atrophy is essentially pathognomic for classical AGS (particularly related to mutations in TREX1 (39)), non-specific white matter disease is much more common (Figure 2B), with, remarkably, AGS-associated genotypes observed to account for ∼10% of 664 genetically confirmed cases of childhood leukodystrophy (40).