Acquisition of liver enzyme elevation in the AGS population. Acquisition of liver enzyme elevation was associated with microcephaly (A; log-rank test, p = 0.0401), disease onset within 3 months of life (B; log-rank test, p = 0.0335), and non-SAMHD1 genotype (C; log-rank test, p = 0.011). ALT, alanine-aminotransferase; AST, aspartate-aminotransferase; GGT, gamma-glutamyl transferase.