The molecular cause of X-ALD are mutations in the ATP-binding cassette subfamily D member 1 (ABCD1) gene, which encodes a peroxisomal transporter mediating the import of coenzyme A-activated very-long-chain fatty acids (VLCFAs) into peroxisomes for degradation2–4. This evidence concerns the gene ABCD1 and X-linked adrenoleukodystrophy.