X-linked adrenoleukodystrophy (X-ALD) is another severe neurometabolic disease characterized by progressive central demyelination, adrenal insufficiency and accumulation of saturated very long-chain fatty acids, and caused by loss of function of the ABCD1 peroxisomal transporter (Ferrer et al., 2010). Here, ABCD1 is linked to X-linked adrenoleukodystrophy.