Before onset of neuroinflammation, median GFAP levels in both asymptomatic X-ALD children/adolescents and AMN patients with progressive myeloneuropathy were higher than in controls of similar age (children/adolescents: median 95.4 [73.3–137.8] vs 65.3 [41.8–76.5] pg/mL; adults: 73.8 [56.2–122.7] vs 53.2 [32.4–78.9] pg/mL; Fig. 2a). Here, GFAP is linked to X-linked adrenoleukodystrophy.