Shoji Tsuji

Tangier disease (TD) is a rare disorder caused by mutations in the ATP‐binding cassette transporter A1 (ABCA1) gene with autosomal recessive inheritance and is characterized by extremely low high‐density lipoprotein cholesterol (HDL‐C) and premature atherosclerosis. Although experimental studies suggest that ABCA1 plays an important role in pancreatic β ‐cell cholesterol homeostasis, its clinical contribution to diabetes development in humans remains unclear. We report a 69‐year‐old Japanese man with early‐onset type 2 diabetes mellitus, profound hypo‐HDL cholesterolemia (HDL‐C 5 mg/dL), and severe atherosclerotic cardiovascular disease. Genetic analysis identified compound heterozygous ABCA1 variants (p.Arg104Cys and the novel p.Asp1706Tyr), both of which were predicted to be potentially pathogenic, although direct functional validation was not performed. Despite a 40‐year duration of diabetes, endogenous insulin secretion was partially preserved. This case highlights phenotypic variability in TD and suggests that variant‐specific effects on ABCA1 function and polygenic susceptibility may influence diabetes development in humans.

Myopathy, lactic acidosis, and sideroblastic anemia type 1 (MLASA1) is an extremely rare mitochondrial disorder caused by biallelic pathogenic variants in PUS1, which encodes a mitochondrial tRNA pseudouridine synthase essential for mitochondrial protein synthesis. We describe two affected siblings presenting with progressive myopathy, lactic acidosis, sideroblastic anemia, short stature, developmental delay, and mild cognitive impairment. Depth-based copy number variation analysis of whole-exome sequencing data revealed a novel homozygous multi-exonic deletion in PUS1. The deletion breakpoints were defined by Sanger sequencing as a 9964 bp deletion spanning part of intron 3 through exons 4–6 and extending into the 3′ untranslated region, resulting in complete loss of the C-terminal coding region. Skeletal muscle histology demonstrated ragged red fibers, whereas immunohistochemistry showed a selective and near-complete loss of NDUFB8, indicating impaired assembly of respiratory chain complex I. A systematic review of previously reported MLASA1 cases revealed marked clinical heterogeneity, including frequent developmental delay, dysmorphic features, and multi-organ involvement. These findings expand the genotypic and phenotypic landscape of MLASA1 and highlight the diagnostic value of copy number variation analysis in unresolved mitochondrial disorders. The impairment of complex I underscores the particular vulnerability of translation-dependent respiratory chain components in PUS1-related diseases.

Autosomal recessive spastic ataxia of Charlevoix-Saguenay, caused by biallelic SACS variants, is classically characterized by spasticity, ataxia, and peripheral neuropathy. The aim of this study was to define the clinical and genetic spectrum of SACS-related inherited peripheral neuropathies (IPNs) in Japanese patients. Targeted gene panel sequencing was performed in 3,353 Japanese cases clinically suspected of having IPN or Charcot-Marie-Tooth (CMT) disease, with PMP22 duplication or deletions pre-excluded in demyelinating subtypes, followed by whole-exome sequencing in a subset of undiagnosed cases. Depth-based copy number variation (CNV) analysis was conducted using CovCopCan or XHMM, with validation by quantitative PCR. Biallelic or putative compound heterozygous SACS variants were identified in 10 index cases, with pathogenic or likely pathogenic variants confirmed in 9 cases (0.268%; 9/3,353). The variant spectrum included frameshift (n = 9), missense (n = 3), and nonsense (n = 2) variants, along with complete SACS gene deletions identified by CNV analysis in 2 cases. Disease onset occurred between 1 and 49 years. All patients exhibited motor and sensory neuropathy, with pyramidal signs observed in 6 patients. Cerebellar ataxia or atrophy was documented in 8 patients. Cognitive impairment was observed in 4 patients, and 1 patient presented with postural hypotension. Most patients showed a length-dependent, sensory-predominant polyneuropathy characterized by slowed nerve conduction velocities. This study defines the contribution of SACS variants in a large case series of Japanese patients with IPN/CMT disease and delineates the heterogeneous genotypic and phenotypic spectrum of SACS-related neuropathies. The high frequency of gene-level deletions underscores the necessity of incorporating CNV analysis into the genetic diagnostic workflow for SACS-related disorders.

[This corrects the article DOI: 10.1212/NXG.0000000000200293.].

Typical MRI findings of vanishing white matter disease (VWM) include diffuse white matter lesions with cystic degeneration. However, mild cases may lack these typical features, posing diagnostic challenges. We describe 2 of 3 individuals carrying the homozygous c.254T >A variant in EIF2B2 identified at our hospital, excluding 1 previously reported case.¹ Genetic analyses were performed using whole-genome sequence or whole-exome sequence analysis, and detected variants were confirmed by direct nucleotide sequence analysis. Brain MRI findings and clinical features were reviewed for the 2 individuals along with other cases in the literature with the same variant. A 69-year-old woman presented with recurrent transient dizziness and secondary amenorrhea. MRI of the brain revealed small T2-hyperintense lesions confined to the subcortical white matter with hyperintensities on diffusion-weighted images and mildly elevated apparent diffusion coefficient values. A 28-year-old woman presented with transient dizziness and secondary amenorrhea. MRI of the brain showed mild T2-hyperintense lesions in the cerebral white matter with frontal predominance. This report highlights the clinically mild cases of VWM with subtle abnormalities on brain MRI who had the homozygous c.254T >A in EIF2B2, further expanding the clinical spectrum of VWM and underscoring the importance of genetic assessments in the diagnosis of individuals with mild clinical and MRI findings.