Retracted : Identification of seven novel mutations in ABCD1 by a DHPLC‐based assay in Italian patients with X‐linked adrenoleukodystrophy

Identification of Two Novel Mutations of ABCD1 Gene in Pedigrees with X-Linked Adrenoleukodystrophy and Review of the Literature

BACKGROUND

X-linked adrenoleukodystrophy (ALD) is an inherited peroxisomal metabolism disorder, resulting 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 the 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 first 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, NM_000033.3 (ABCD1): c.874_876delGAG (p.Glu292del) and NM_000033.3 (ABCD1): 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 heterozygous 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.

A Large Family with p.Arg554His Mutation in ABCD1: Clinical Features and Genotype/Phenotype Correlation in Female Carriers

X-linked adrenoleukodystrophy (X-ALD, OMIM #300100) is the most common peroxisomal disorder clinically characterized by two main phenotypes: adrenomyeloneuropathy (AMN) and the cerebral demyelinating form of X-ALD (cerebral ALD). The disease is caused by defects in the gene for the adenosine triphosphate (ATP)-binding cassette protein, subfamily D (ABCD1) that encodes the peroxisomal transporter of very-long-chain fatty acids (VLCFAs). The defective function of ABCD1 protein prevents β-oxidation of VLCFAs, which thus accumulate in tissues and plasma, to represent the hallmark of the disease. As in many X-linked diseases, it has been routinely expected that female carriers are asymptomatic. Nonetheless, recent findings indicate that most ABCD1 female carriers become symptomatic, with a motor disability that typically appears between the fourth and fifth decade. In this paper, we report a large family in which affected males died during the first decade, while affected females develop, during the fourth decade, progressive lower limb weakness with spastic or ataxic-spastic gait, tetra-hyperreflexia with sensory alterations. Clinical and genetic evaluations were performed in nine subjects, eight females (five affected and three healthy) and one healthy male. All affected females were carriers of the c.1661G>A (p.Arg554His, rs201568579) mutation. This study strengthens the relevance of clinical symptoms in female carriers of ABCD1 mutations, which leads to a better understanding of the role of the genetic background and the genotype-phenotype correlation. This indicates the relevance to include ABCD1 genes in genetic panels for gait disturbance in women.

Late adult-onset adrenomyeloneuropathy evolving with atypical severe frontal lobe syndrome: Importance of neuroimaging

X-linked adrenoleukodystrophy (X-ALD) is a rare inherited metabolic disease affecting the nervous system and the adrenal glands. It is caused by a mutation of the ABCD1 gene, resulting in the impaired degradation of very long-chain fatty acids and their subsequent accumulation in several organs and tissues. X-ALD is notable for its high phenotypical variability, that includes isolated adrenocortical insufficiency, slowly progressive myelopathy with paraparesis, ataxia, and peripheral neuropathy to severe childhood cerebral forms.

Here, we describe the case of an X-ALD patient with a p.Gly343Val mutation in ABCD1 gene, who presented in adulthood with a spinal syndrome of mild severity, and later developed a progressive cognitive and behavioral syndrome. Our patient showed a striking correlation between clinical phenotype and neuroimaging, including a brain fluoro-2-deoxy-d-glucose positron emission tomography that displayed an atypical cerebral glucose metabolism.

Prenatal diagnosis of X-linked adrenoleukodystrophy associated with isolated pericardial effusion

This is the first reported case of fetal pericardial effusion in association with X-linked adrenoleukodystrophy and hypocortisolism from a nonautoimmune cause. Our hypothesis is that in experienced hands and after accurate genetic counseling, isolated pericardial effusion can constitute an indication for a severe metabolic disease.

Denaturing HPLC for mutation screening

Denaturing High-Performance Liquid Chromatography (dHPLC) is probably the most versatile and one of the most widely used mutation screening technologies. It benefits from a combination of relative technical simplicity and a very high sensitivity (mutation detection rate), approaching 100%. DHPLC can reliably detect single-base mismatches in fragments between 150 and 500 bp, although detection in fragments up to 1,500 bp has been reported. The ability of dHPLC to detect both known and unknown mutations/SNPs, and its' high sensitivity and specificity (reproducibility) has put this technology at the forefront of genetic analysis for a wide variety of diseases.

Mutational analyses of Taiwanese kindred with X-linked adrenoleukodystrophy

X-linked adrenoleukodystrophy is a neurodegenerative disorder with highly variable clinical presentation, including the childhood cerebral form, adult form adrenomyeloneuropathy, and Addison disease. The biochemical hallmark of the disorder is the accumulation of saturated very long chain fatty acids in all tissues and body fluids. This accumulation results from mutations in the ABCD1 gene localized to Xq28. Using polymerase chain reaction and direct sequencing of deoxyribonucleic acid, we identified five novel mutations, including a microdeletion (1624 del ATC), a splicing site mutation (intervening sequence 1 [IVS1] -2a>c), and three missense mutations (1172 T>C, 1520 G>A, and 1754 T>C), from Taiwanese kindred with X-linked adrenoleukodystrophy. A polymorphism involving a single nucleotide deletion in the intervening sequence 5 (IVS5 -6 del c) of the ABCD1 gene, previously misattributed as a mutation in the Chinese population, was also identified. The dinucleotide deletion (1415 del AG) mutation common in Japan and Western countries was not found as frequently in the Chinese and Taiwanese populations. Instead, a higher mutation frequency was observed in exon 6 of the ABCD1 gene among Japanese, Chinese, and Taiwanese kindred with X-linked adrenoleukodystrophy, representing a potential mutational hotspot for future mutational screening among these Asian populations.