X-ALD results from a loss of function by the peroxisomal ABCD1 fatty acid transporter, resulting in VLCFAs accumulation in the target organs and plasma caused by impaired VLCFAs import into the peroxisome, which decreases the peroxisomal beta-oxidation enzyme substrate [19, 83, 85, 88]. Here, ABCD1 is linked to X-linked adrenoleukodystrophy.