ACOX1 and X-linked adrenoleukodystrophy: For instance, X-linked adrenoleukodystrophy is associated with mutations in the ATP-binding cassette transporter D1 (ABCD1) gene and ACOX1 deficiency with mutations in the acyl-CoA oxidase 1 (ACOX1) gene, which controls the rate-limiting step of peroxisomal β-oxidation [16].