Adrenoleukodystrophy (ALD) is a rare X-linked genetic metabolic disorder characterized by the accumulation of very long chain fatty acids (VLCFA) within the adrenal glands, as well as the central and peripheral nervous systems. Adult-onset ALD is particularly uncommon and easily misdiagnosed. The objective of this study is to facilitate the early diagnosis and treatment of adult-onset ALD. Seven adult-onset ALD patients of Chinese descent were enrolled in the study. Detailed clinical characteristics, laboratory results, imaging findings and genetic testing of the patients were collected and analyzed. All seven patients diagnosed with adult-onset ALD were male, including two with adult cerebral ALD (ACALD), one with adrenomyeloneuropathy (AMN), and four presenting with the spinocerebellar variant. The primary clinical manifestations of the two ACALD patients were progressive cognitive dysfunction and psychiatric symptoms. The AMN patient showed chronic progressive spastic paraplegia and displayed non-specific thoracic spinal cord atrophy on MRI. Symptoms observed in the four patients with spinocerebellar variant included cerebellar ataxia, dysarthria, spastic paraplegia, peripheral neuropathy, sphincter dysfunction, and alopecia. These four patients all demonstrated symmetrical white matter hyperintensity (WMH) in the cerebellum on brain magnetic resonance imaging (MRI). Additionally, two of these patients exhibited abnormal MRI signals in the pyramidal tract. All the patients had an elevation of VLCFAs, which is diagnostic for ALD. One patient exhibited elevated adrenocorticotropic hormone (ACTH) and decreased cortisol levels, while six patients displayed slightly elevated ACTH levels and normal cortisol levels without any clinical signs of adrenal insufficiency. Genetic testing identified four known ABCD1 pathogenic variants as well as two novel pathogenic variants. Progressive cognitive impairment and behavioral abnormalities are common clinical manifestations of ACALD. AMN and the spinocerebellar variant are prevalent phenotypes of adult-onset ALD. Patients with adult-onset ALD may present with isolated WMH in the cerebellum on brain MRI. Routine screening for ALD should be conducted in male patients diagnosed with Addison's disease. Subclinical adrenal cortex insufficiency is a common finding in adult-onset ALD. Elevated levels of VLCFA function as a reliable clinical biomarker for ALD. The identification of novel pathogenic variants in ABCD1 broadens the genetic spectrum of ALD.

Pathogenic variants in B-cell receptor-associated protein (BCAP31) are associated with X-linked, deafness, dystonia and cerebral hypomyelination (DDCH) syndrome. DDCH is congenital and non-progressive, featuring severe intellectual disability (ID), variable dysmorphism, and sometimes associated with shortened survival. BCAP31 encodes one of the most abundant chaperones, with several functions including acting as a negative regulator of endoplasmic reticulum (ER) calcium ion (Ca2+) concentration. Here, we characterize an X-linked syndrome, its underlying genotype, and a functional evaluation of the identified candidate genetic variant. Evaluation of motor features, neuroimaging studies, neurophysiological, and cognitive tests. Whole exome sequencing (WES) was applied, a plasmid encoding BCAP31 with and without a candidate variant was transfected into SH-SY5Y cells to assess subcellular location and to measure Ca2+ levels in the cytoplasm. Adult-onset ataxia, cognitive impairment, and hearing loss leading to deafness are the predominant features. Reduced penetrance, slow progression with preserved ability to walk in advance age, and universal cerebellar atrophy are other features for this syndrome. This condition is associated with the new variant c.22G>A (V8I) in BCAP31 at Xq28. The subcellular location of the V8I BCAP31 protein was not altered but caused significant elevation of cytosolic Ca2+. Our findings expand the spectrum of variants in BCAP31 from neurodevelopmental syndromes to include a progressive neurodegenerative disease with variable expressivity. This is the first time ataxia is described in association with a BCAP31 variant and functional evidence of pathogenicity is provided. Additional BCAP31 cases featuring ataxia are needed to establish an association. © 2025 The Author(s). Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Mutations in the X-linked endosomal Na+/H+ exchanger 6 (NHE6) cause Christianson syndrome (CS). Here, in the largest study to date, we examine genetic diversity and clinical progression in CS into adulthood. Data were collected as part of the International Christianson Syndrome and NHE6 (SLC9A6) Gene Network Study. 44 individuals with 31 unique NHE6 mutations, age 2-32 years, were followed prospectively, herein reporting baseline, 1 year follow-up and retrospective natural history. We present data on the CS phenotype with regard to physical growth and adaptive and motor regression across the lifespan including information on mortality. Longitudinal data on body weight and height were examined using a linear mixed model. The rate of growth across development was slow and resulted in prominently decreased age-normed height and weight by adulthood. Adaptive functioning was longitudinally examined; a majority of adult participants (18+ years) lost gross and fine motor skills over a 1 year follow-up. Previously defined core diagnostic criteria for CS (present in>85%)-namely non-verbal status, intellectual disability, epilepsy, postnatal microcephaly, ataxia, hyperkinesia-were universally present in age 6-16; however, an additional core feature of high pain tolerance was added (present in 91%). While neurologic examinations were consistent with cerebellar dysfunction, importantly, a majority of individuals (>50% older than 10) also had corticospinal tract abnormalities. Three participants died during the period of the study. In this large and longitudinal study of CS, we begin to define the trajectory of symptoms and the adult phenotype thereby identifying critical targets for treatment.

The functional integrity of the central nervous system relies on complex mechanisms in which the mitochondria are crucial actors because of their involvement in a multitude of bioenergetics and biosynthetic pathways. Mitochondrial diseases are among the most prevalent groups of inherited neurological disorders, affecting up to 1 in 5000 adults and despite considerable efforts around the world there is still limited curative treatments. Harlequin mice correspond to a relevant model of recessive X-linked mitochondrial disease due to a proviral insertion in the first intron of the Apoptosis-inducing factor gene, resulting in an almost complete depletion of the corresponding protein. These mice exhibit progressive degeneration of the retina, optic nerve, cerebellum, and cortical regions leading to irremediable blindness and ataxia, reminiscent of what is observed in patients suffering from mitochondrial diseases. We evaluated the progression of cerebellar degeneration in Harlequin mice, especially for Purkinje cells and its relationship with bioenergetics failure and behavioral damage. For the first time to our knowledge, we demonstrated that Harlequin mice display cognitive and emotional impairments at early stage of the disease with further deteriorations as ataxia aggravates. These functions, corresponding to higher-order cognitive processing, have been assigned to a complex network of reciprocal connections between the cerebellum and many cortical areas which could be dysfunctional in these mice. Consequently, Harlequin mice become a suitable experimental model to test innovative therapeutics, via the targeting of mitochondria which can become available to a large spectrum of neurological diseases.

Hereditary dominant ataxias are a heterogeneous group of neurodegenerative conditions causing cerebellar dysfunction and characterized by progressive motor incoordination. Despite many efforts put into the study of these diseases, there are no effective treatments yet. Zebrafish models are widely used to characterize neuronal disorders due to its conserved vertebrate genetics that easily support genetic edition and their optic transparency that allows observing the intact CNS and its connections. In addition, its small size and external fertilization help to develop high throughput assays of candidate drugs. Here, we discuss the contributions of zebrafish models to the study of dominant ataxias defining phenotypes, genetic function, behavior and possible treatments. In addition, we review the zebrafish models created for X-linked repeat expansion diseases X-fragile/fragile-X tremor ataxia. Most of the models reviewed here presented neuronal damage and locomotor deficits. However, there is a generalized lack of zebrafish adult heterozygous models and there are no knock-in zebrafish models available for these diseases. The models created for dominant ataxias helped to elucidate gene function and mechanisms that cause neuronal damage. In the future, the application of new genetic edition techniques would help to develop more accurate zebrafish models of dominant ataxias.