ABCD1 and X-linked adrenoleukodystrophy: X-ALD, the most frequent peroxisomal disorder, is associated with mutations in the ABCD1 gene and is characterized by an impaired peroxisomal β-oxidation pathway and very long-chain fatty acid (VLCFA) accumulation in plasma and tissues of patients (Mosser et al., 1993; Trompier and Savary, 2013; Kemp et al., 2016).