Adrenoleukodystrophy siblings with a novel ABCD1 missense variant presenting with phenotypic differences: a case report and literature review

From gene to therapy: a review of deciphering the role of ABCD1 in combating X-Linked adrenoleukodystrophy

X-linked adrenoleukodystrophy (X-ALD) is a severe genetic disorder caused by ABCD1 mutations, resulting in the buildup of very-long-chain fatty acids, leading to significant neurological decline and adrenal insufficiency. Despite advancements in understanding the mechanisms of X-ALD, its pathophysiology remains incompletely understood, complicating the development of effective treatments. This review provides a comprehensive overview of X-ALD, with a focus on the genetic and biochemical roles of ABCD1 and the impacts of its mutations. Current therapeutic approaches are evaluated, discussing their limitations, and emphasizing the need to fully elucidate the pathogenesis of X-ALD. Additionally, this review highlights the importance of international collaboration to enhance systematic data collection and advance biomarker discovery, ultimately improving patient outcomes with X-ALD.

A female adult-onset X-ALD patient with pure cerebellar symptoms:a case report

X-linked adrenoleukodystrophy (X-ALD) caused by ATP-binding cassette subfamily D member 1 (ABCD1) gene defects is the most common inherited peroxisomal disorder.The female cerebello-brainstem dominant type in which cerebellum and brainstem are mainly involved is very rare. We report a 40-year-old female who was diagnosed as the rare disorder with magnetic resonance imaging (MRI) and genetic analysis mainly. Her initial symptoms were progressive slurred speech and writing disturbance. Her brain MRI showed obvious atrophy of brainstem and cerebellum. She did not have adrenal insufficiency. Genetic analysis showed a heterozygous missense mutation in exon 4 of the coding region of ABCD1 (c.1252C > T, p.Arg418Trp).This is the first report of this particular mutation being associated with the cerebello-brainstem dominant phenotype of X-ALD, as well as the first description of this X-ALD variant in a (heterozygous) female patient.X-ALD should be considered in young and middle-aged patients with slow-progressing ataxia and dysarthria.

Brainstem dominant form of X-linked adrenoleukodystrophy with a novel ABCD1 missense variant: A case report and literature review

BACKGROUND

X-linked adrenoleukodystrophy (X-ALD) is the most common peroxisomal disorder attributed to ABCD1 mutations. Case reports with predominant brainstem involvement are rare.

CASE PRESENTATION

In this study, we reported a plateau male worker of X-ALD characterized by progressive weakness accompanied by gait instability, mild nystagmus, and constipation. After 2 years of onset, a brain Magnetic Resonance Image (MRI) scan showed no abnormality but genetic analysis revealed a heterozygous mutation (c.1534G>A) in the ABCD1 gene. After 7 years of onset, although the patient was given aggressive dietary and symptomatic treatment in the course of the disease, a brain MRI scan showed predominantly brainstem damage, but serum concentrations of very long-chain fatty acids were normal, and he had been bedridden for almost 2 years with severe bladder dysfunction, forcing him to undergo cystostomy. The patient was discharged with improved urinary retention and renal function.

CONCLUSIONS

We reported an X-ALD patient with a novel ABCD1 variation characterized by brainstem damage and retrospectively summarized the clinical manifestation, MRI features, and genetic features of X-ALD patients with brainstem damage.

Cerebello-brainstem dominant form of X-linked adrenoleukodystrophy with intrafamilial phenotypic variability

Objectives

This study aimed to describe the clinical and radiological characteristics of a cerebello-brainstem dominant form of X-linked adrenoleukodystrophy (X-ALD).

Methods

Three affected members from a family with cerebellar ataxia received full neurological, laboratory and radiological examinations. Genetic diagnoses were confirmed using whole-exome sequencing and protein structural modeling.

Results

All affected members presented with slurred speech, ataxia, and spasticity, but showed obvious differences in phenotypic severity and radiological findings. The levels of very long-chain fatty acids (VLCFA) were elevated in each member, while only one had adrenal dysfunction. Genetic analysis identified a hemizygous missense mutation (c.887A>G, p.Tyr296Cys) of the ATP-binding cassette subfamily D member 1 gene (ABCD1) in all affected members, which is likely to destabilize the overall structure of the ABCD1 protein.

Conclusions

We report a cerebello-dominant form of X-ALD caused by a missense variant in ABCD1. This report highlights intrafamilial phenotypic variability in X-ALD.

High incidence of null variants identified from newborn screening of X-linked adrenoleukodystrophy in Taiwan

Background

Adrenoleukodystrophy (ALD) is an X-linked peroxisomal disorder caused by variants in the ABCD1 gene and can lead to Addison disease, childhood cerebral ALD, or adrenomyeloneuropathy. Presymptomatic hematopoietic stem cell transplantation is the only curative treatment for the disease and requires early detection through newborn screening (NBS) and close follow-up.

Methods

An NBS program for ALD was performed by a two-tiered dried blood spot (DBS) lysophosphatidylcholine C26:0 (C26:0-LPC) concentration analysis. ABCD1 sequencing was eventually added as a third-tier test, and whole exome sequencing was used to confirm the diagnosis of all peroxisomal diseases. Affected newborns were followed-up for adrenal insufficiency and cerebral white matter abnormalities.

Results

We identified 12 males and 10 females with ABCD1 variants, and 3 patients with Zellweger syndrome from 320,528 newborns. Eight (36.4%) ABCD1 variants identified in the current study were null variants, but there were no hotspots or founder effect. During a median follow-up period of 2.28 years, two (16.7%) male patients with ABCD1 variants developed Addison's disease. Extended family screening revealed one 28-year-old asymptomatic hemizygous father of a null variant (c.678delC). Among the three with Zellweger syndrome, one died at the age of 3 months, one showed developmental delay at the age of 1 year, and one was lost to follow-up.

Conclusion

Screening for ALD has been added to the NBS program in Taiwan with a high degree of success. The screening algorithm revealed a high proportion of null variants in cases found by NBS in Taiwan, a subset of patients who may have earlier disease onset. We also demonstrate the feasibility of combining the diagnosis of ALD and other peroxisomal disorders into one screening algorithm.

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We report our screening results of a successful newborn screening for adrenoleukodystrophy in Taiwan since November 2016.

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C26:0-LPC levels at newborn screening tended to be higher in males with null variants than those with missense variants.

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A higher proportion of ALD patients carry null variants in Taiwan,and may have earlier onset or more severe phenotypes.

ABCD1 Gene Mutations: Mechanisms and Management of Adrenomyeloneuropathy

Pathogenic variants in the ABCD1 gene on the X chromosome may result in widely heterogenous phenotypes, including adrenomyeloneuropathy (AMN). Affected males typically present in their third or fourth decade of life with progressive lower limb weakness and spasticity, and may develop signs and symptoms of adrenal insufficiency and/or cerebral demyelination. Heterozygous females may be asymptomatic, but may develop a later-onset and more slowly progressive spastic paraparesis. In this review, we describe the clinical presentation of AMN, as well as its diagnosis and management. The role of rehabilitative therapies and options for management of spasticity are highlighted.