Interestingly, in 17 out of 22 assessable X-ALD carriers (Table 1), we observed a significant positive correlation between the degree of mutant ABCD1 expression and the plasma concentration of C26:0 (p = 0.0201; Spearman ρ correlation) or the ratio C26:0 to C22:0 (p = 0.0141). This evidence concerns the gene ABCD1 and adrenoleukodystrophy.