ABCD1 and X-linked adrenoleukodystrophy: All patients with X-ALD have mutations in the ABCD1 gene in Xq28, which encodes the peroxisomal adrenoleukodystrophy protein (ALDP or ABCD1) [26, 66]; ALDP transports very long-chain fatty acids (VLCFA) or VLCFA–CoA esters into the peroxisome for degradation by β-oxidation [93].