Clinical, neuroimaging, biochemical, and genetic features in six Chinese patients with Adrenomyeloneuropathy

Adult-onset leukodystrophies: a practical guide, recent treatment updates, and future directions

Adult-onset leukodystrophies though individually rare are not uncommon. This group includes several disorders with isolated adult presentations, as well as several childhood leukodystrophies with attenuated phenotypes that present at a later age. Misdiagnoses often occur due to the clinical and radiological overlap with common acquired disorders such as infectious, immune, inflammatory, vascular, metabolic, and toxic etiologies. Increased prevalence of non-specific white matter changes in adult population poses challenges during diagnostic considerations. Clinico-radiological spectrum and molecular landscape of adult-onset leukodystrophies have not been completely elucidated at this time. Diagnostic approach is less well-standardized when compared to the childhood counterpart. Absence of family history and reduced penetrance in certain disorders frequently create a dilemma. Comprehensive evaluation and molecular confirmation when available helps in prognostication, early initiation of treatment in certain disorders, enrollment in clinical trials, and provides valuable information for the family for reproductive counseling. In this review article, we aimed to formulate an approach to adult-onset leukodystrophies that will be useful in routine practice, discuss common adult-onset leukodystrophies with usual and unusual presentations, neuroimaging findings, recent advances in treatment, acquired mimics, and provide an algorithm for comprehensive clinical, radiological, and genetic evaluation that will facilitate early diagnosis and consider active treatment options when available. A high index of suspicion, awareness of the clinico-radiological presentations, and comprehensive genetic evaluation are paramount because treatment options are available for several disorders when diagnosed early in the disease course.

Novel mutations in the ABCD1 gene caused adrenomyeloneuropathy in the Chinese population

Background

As a rare genetic disease, adrenomyeloneuropathy (AMN) is the most common adult phenotype of X-linked adrenoleukodystrophy (X-ALD). Mutations in the ABCD1 gene have been identified to cause AMN.

Methods

We applied clinical evaluation, laboratory tests, and neuroimaging on three patients with progressive spastic paraparesis. In genetic analysis, we investigated ABCD1 gene mutations by whole-exome sequencing and Sanger sequencing. Bioinformatics tools were used to predict the effects of identified ABCD1 mutations on the protein.

Results

All three patients were men with adult-onset disease, mainly characterized by progressive spastic paraparesis. Among them, two patients had peripheral neuropathy and one patient had signs of adrenal insufficiency. All three patients showed cerebral involvement on brain MRI, while two patients were found with diffuse cord atrophy on spinal MRI. High-VLCFA levels in plasma, as well as C24:0/C22:0 and C26:0/C22:0 ratios, were found in all three patients. In addition, three different ABCD1 mutations were identified in three unrelated Chinese families, including one known mutation (c.1415_1416delAG) and two novel mutations (c.217C>T and c.160_170delACGCAGGAGGC). Based on the clinical assessment, radiographic, biochemical, and genetic testing, the final diagnosis was AMN in these patients with spastic paraparesis.

Conclusion

This study reported three patients with AMN and identified two novel mutations in the ABCD1 in the Chinese population. Our finding emphasized that X-ALD is an important cause of adult-onset spastic paraplegia. Thus, neuroimaging, VLCFA testing, and especially the detection of the ABCD1 gene have important implications for the etiological diagnosis of adult patients with spastic paraplegia.

Nuclear Factor Erythroid-2-Related Factor 2 Signaling in the Neuropathophysiology of Inherited Metabolic Disorders

Inherited metabolic disorders (IMDs) are rare genetic conditions that affect multiple organs, predominantly the central nervous system. Since treatment for a large number of IMDs is limited, there is an urgent need to find novel therapeutical targets. Nuclear factor erythroid-2-related factor 2 (Nrf2) is a transcription factor that has a key role in controlling the intracellular redox environment by regulating the expression of antioxidant enzymes and several important genes related to redox homeostasis. Considering that oxidative stress along with antioxidant system alterations is a mechanism involved in the neuropathophysiology of many IMDs, this review focuses on the current knowledge about Nrf2 signaling dysregulation observed in this group of disorders characterized by neurological dysfunction. We review here Nrf2 signaling alterations observed in X-linked adrenoleukodystrophy, glutaric acidemia type I, hyperhomocysteinemia, and Friedreich’s ataxia. Additionally, beneficial effects of different Nrf2 activators are shown, identifying a promising target for treatment of patients with these disorders. We expect that this article stimulates research into the investigation of Nrf2 pathway involvement in IMDs and the use of potential pharmacological modulators of this transcription factor to counteract oxidative stress and exert neuroprotection.

Investigating ABCD1 mutations in a Taiwanese cohort with hereditary spastic paraplegia phenotype

BACKGROUND

Adrenoleukodystrophy (ALD) is an X-linked peroxisomal disorder caused by mutations in the ABCD1 gene. The clinical manifestations of ALD vary widely with some patients presenting with adrenomyeloneuropathy (AMN) that resembles the phenotype of hereditary spastic paraplegia (HSP). The aim of this study is to investigate the frequency, spectrum, and clinical features of ABCD1 mutations in Taiwanese patients with HSP phenotype.

METHODS

Mutational analysis of the ABCD1 gene was performed in 230 unrelated Taiwanese patients with clinically suspected HSP by targeted resequencing. Clinical, electrophysiological, and neuroimaging features of the patients carrying an ABCD1 pathogenic mutation were characterized.

RESULTS

Ten different ABCD1 mutations were identified in eleven patients, including two novel mutations (p.Q177Pfs*17 and p.Y357*) and eight ever reported in ALD cases of other ethnicities. All patients were male and exhibited slowly progressive spastic paraparesis with onset ages ranging from 21 to 50 years. Most of them had additional non-motor symptoms, including autonomic dysfunction in nine patients, sensory deficits in seven, premature baldness in seven, skin hyperpigmentation in five, psychiatric symptoms in one and cerebellar ataxia in one. Seven of the ten patients who ever received nerve conduction studies showed axonal polyneuropathy. Magnetic resonance imaging (MRI) revealed diffuse spinal cord atrophy in seven patients, cerebral white matter hyperintensity in one patient, and cerebellar involvement in one patient.

CONCLUSIONS

ABCD1 mutations account for 4.8% (11/230) of the cases with HSP phenotype in Taiwan. This study highlights the importance to consider ABCD1 mutations in patients with clinically suspected HSP of unknown genetic causes.

X-linked adrenoleukodystrophy caused by a novel mutation presenting with various phenotypes in a Taiwanese family

X-linked adrenoleukodystrophy (X-ALD) is a peroxisomal disorder that primarily affects the white matter of central nervous system and the adrenal cortex. It is caused by mutations in the adenosine triphosphate-binding cassette, subfamily D, member 1 (ABCD1) gene that results in elevated plasma levels of very long chain fatty acids (VLCFAs). The disease is characterized by an unpredictable variation in phenotypic expressions, including childhood cerebral form (CCALD) and adrenomyeloneuropathy (AMN). Genetic analysis is a reliable method for the diagnosis of X-ALD. We reported a 46-year-old male admitted to Department of Neurology, Chang Gung Memorial Hospital with progressive paraparesis and Addison's disease, which was diagnosed when he was around 20-year-old. Plasma levels of VLCFA showed that his C26:0, C24:0/C22:0 and C26:0/C22:0 ratios were significantly elevated. A novel missense mutation (p.Arg163Cys) caused by the nucleotide change c.487C > T in exon 1 was identified in the ABCD1 gene of the proband and his subclinical family members. In this article, we reviewed the mutations that had been reported at the same position with different phenotypes. Given that the nerve conduction study (NCS) of the proband demonstrated a rare finding of demyelinating polyneuropathy with conduction blocks, we also reviewed the findings of NCS in patients with AMN in literature.

A novel ABCD1 G1202A mutation in a Chinese patient with pure adrenomyeloneuropathy and literature review

Adrenomyeloneuropathy (AMN) is a kind of varied disease caused by ABCD1 gene mutation and characterized by very-long-chain fatty acids (VLCFA) accumulation. It is diagnosed by clinical features, high VLCFAs levels and ABCD1 gene mutation. AMN is rarely reported in Chinese population. In this study, we report the genetic and clinical features of a Chinese pure AMN patient. Meanwhile, we conducted a literature review of AMN cases to summarize the characteristics of AMN. We report a rare Chinese pure AMN case with slowly progressive weakness of the lower extremities, caused by a novel c.1202G > A mutation in ABCD1 gene. The literature review indicates that spastic paraplegia is the mainly clinical manifestation in patients with AMN. VLCFAs and ABCD1 gene test should be performed in patients with spastic paraplegia of the lower limbs to diagnose AMN.