Peroxisomal single enzyme deficiencies include among others, acyl-CoA oxidase deficiency (Ferdinandusse et al., 2007), ACBD5 deficiency (Ferdinandusse et al., 2017), and the most common peroxisomal disorder, adrenoleukodystrophy (ALD) (Moser et al., 2001). Here, ACBD5 is linked to X-linked adrenoleukodystrophy.