Adrenoleukodystrophy (ALD)
https://www.sciencedirect.com/science/article/abs/pii/S0009898120305854
ALD is caused by mutations in the gene ABCD1, which contains the instructions for making a protein known as ABCD1 (adenosine triphosphate-binding cassette, subfamily D). In this study, researchers in Taiwan describe the symptoms of a male ALD patient who has a mutation in ABCD1 never previously observed in any ALD patient. The patient was found to have increased levels of a type of biological molecule known as ‘very long chain fatty acids’, an observation indicative of ALD. In this article, the researchers discuss in detail something known as ‘genotype–phenotype correlation’. A genotype is a term used to refer to an individual’s genetic identity. In this paper, for example, genotype means the version of the ABCD1 gene a person affected by ALD possesses. A ‘phenotype’ is then the physical manifestation a genotype. In this context, the phenotype is the consequence of the ABCD1 mutation, i.e., the set of symptoms an individual carrying a mutation in ABCD1 experiences. In some conditions, there may be a correlation between genotype and phenotype. For example, patients with mutations in a certain part of a gene may experience more severe disease. However, this is not the case in ALD. Knowledge of where a given mutation occurs in the gene may not be used to predict how severe a disease might be, and individuals with the same mutation may experience different symptoms. The reasons for this are currently unknown, and research into why individuals with the same ABCD1 mutations are affected so differently is ongoing.