NEFL and X-linked adrenoleukodystrophy: Thus, focusing on childhood/adolescent X-ALD patients, we evaluated the prognostic value of blood NfL to evidence CALD-indicative demyelination, without prior knowledge of clinical neuroimaging-based assessment, in a plasma validation set from phenotype-blinded X-ALD patients (n = 25; aged 4–13 years, median age = 6 years; details in Supplementary Table S2).