Mutational analysis of X-linked adrenoleukodystrophy gene

X-linked adrenoleukodystrophy (ALD) is an inherited peroxisomal disorder characterized by progressive neurological dysfunction, occasionally associated with adrenal insufficiency. The clinical phenotypes of ALD are quite variable, and include childhood ALD, adult-onset ALD, adrenomyeloneuropathy, and Addison's disease only. Although the causative gene for ALD has been identified, the physiological role of the gene product remains to be clarified. Despite many mutations having been identified in patients with these clinical phenotypes, the genotype-phenotype correlations have not been clarified. The authors investigated genotype-phenotype correlations in ALD by analyses on 29 unrelated Japanese patients with ALD and by a review of the literature. All the phenotypes were associated with mutations leading to protein truncation, as well as those resulting in subtle amino acid changes. Furthermore, there were no differences in phenotypic expression among the natures of the subtle amino acid changes. All these data indicate that no obvious correlations exist between the phenotypes of ALD patients and their genotypes, suggesting that other genetic or environmental factors may also be involved in determining phenotypic expression in ALD.