There is no phenotype/genotype correlation as all forms of ALD occur with the same mutation in the ABCD1 gene, within the same kindred and even differing time of onset in monozygotic twins (Di Rocco, Doria‐Lamba, & Caruso, 2001; Korenke et al., 1996). This evidence concerns the gene ABCD1 and X-linked adrenoleukodystrophy.