ABCA4 and X-linked adrenoleukodystrophy: Adrenoleukodystrophy (X-ALD) is a rare X-linked disease of peroxisomal oxidation caused by variants in the ABCD1 gene [31], encoding for an ATP-binding cassette transporter for very long chain fatty acids (VLCFA) that mediates the influx into peroxisomes for β-oxidation, with more than 2500 known variants [32].