X-linked adrenoleukodystrophy (X-ALD) is the most common peroxisomal disorder and is caused by mutations or large deletions of one or more exons in the ABCD1 gene located in Xq28, which encodes the peroxisomal member of the ATP-binding cassette (ABC) transporter subfamily D member 1 (ABCD1), also known as adrenoleukodystrophy protein (ALDP) [1], [2]. The gene discussed is ABCD1; the disease is peroxisomal disease.