ALD is caused by a mutation in the ABCD1 gene which encodes a peroxisomal ATP‐binding cassette transporter for very long‐chain saturated fatty acids ≥ C22:0 (VLCFA) into the peroxisome for β‐oxidation (Kemp et al., 2001). The gene discussed is ABCD1; the disease is X-linked adrenoleukodystrophy.