Identification of Two Novel Mutations of ABCD1 Gene in Pedigrees With X‐linked Adrenoleukodystrophy and Review of the Literatures

Abstract

Background

X-linked adrenoleukodysrophy (ALD) is an inherited peroxisomal metabolism disorder, results from the loss-of-function mutation of ATP-binding cassette protein subfamily D1 ( ABCD1 ) gene. The dysfunction of ALD protein, a peroxisomal ATP-binding cassette transporter, results in the excessive saturated very long chain fatty acids (VLCFAs) accumulation in organs including brain, spine and adrenal cortex. X-ALD is characterized as the childhood, adolescent, adult cerebral ALD, adrenomyeloneuropathy (AMN), adrenal insufficiency, and asymptomatic phenotypes, exhibiting a high variety of clinical neurological manifestations with or without adrenocortical insufficiency.

Results

In this study, we reported two cases of X-ALD, which were firstly diagnosed as adrenal insufficiency (Addison’s disease) and treated with adrenocortical supplement. However, both of the cases progressed as neurological symptoms and signs after decades. Elevated VLCFAs level, brain MRI scan and genetic analysis confirmed final diagnosis. In addition, we identified two novel mutations of ABCD1 gene, c.874_876delGAG (p.Glu292del) and c.96_97delCT (p.Tyr33Profs*161) in exon 1 of ABCD1 gene. Sanger sequencing confirmed that the proband’s mother of the first case was hemizygous carrying the same variant. Adrenal insufficiency-only type is very rare, however, it may be the starting performance of X-ALD. In addition, we summarized reported mutation sites and clinical manifestations to investigate the correlationship of phenotype-genotype of X-ALD.

Conclusions

The early warning manifestations should be noticed, and the probability of X-ALD should be considered. This report could be beneficial for the early diagnosis and genetic counseling for patients with X-ALD.

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