To better understand the molecular changes in the leukodystrophies group, which are primarily characterized by cellular dysfunction at the level of glial cells, it is essential to assess and characterize biomarkers related to the main pathological process, as exemplified by the analysis of glial fibrillary acidic protein (GFAP) as a biomarker of astrocytic dysfunction in X-linked adrenoleukodystrophy, metachromatic leukodystrophy, and Alexander disease [52,53,54]. Here, GFAP is linked to X-linked adrenoleukodystrophy.