Clinicopathological-genetic features of congenital myasthenic syndrome from a Chinese neuromuscular centre.

Congenital myasthenic syndrome (CMS) encompasses a heterogeneous group of inherited disorders affecting nerve transmission across the neuromuscular junction. The aim of this study was to characterize the clinical, physiological, pathohistological and genetic features of nine unrelated Chinese patients with CMS from a single neuromuscular centre. A total of nine patients aged from neonates to 34 years were enrolled who exhibited initial symptoms. Physical examinations revealed that all patients exhibited muscle weakness. Muscle biopsies demonstrated multiple myopathological changes, including increased fibre size variation, myofibrillar network disarray, necrosis, myofiber grouping, regeneration, fibre atrophy and angular fibres. Genetic testing revealed six different mutated genes, including AGRN (2/9), CHRNE (1/9), GFPT1 (1/9), GMPPB (1/9), PLEC (3/9) and SCN4A (1/9). In addition, patients exhibited differential responses to pharmacological treatment. Prompt utilization of genetic testing will identify novel variants and expand our understanding of the phenotype of this rare syndrome. Our findings contribute to the clinical, pathohistological and genetic spectrum of congenital myasthenic syndrome in China.

Findings of limb-girdle muscular dystrophy R7 telethonin-related patients from a Chinese neuromuscular center.

Limb-girdle muscular dystrophy (LGMD) is a group of clinically and genetically heterogeneous neuromuscular disorders. LGMD-R7, which is caused by telethonin gene (TCAP) mutations, is one of the rarest forms of LGMD, and only a small number of LGMD-R7 cases have been described and mostly include patients from Brazil. A total of two LGMD-R7 patients were enrolled at a Chinese neuromuscular center. Demographic and clinical data were collected. Laboratory investigations and electromyography were performed. Routine and immunohistochemistry staining of muscle specimens was performed, and a next-generation sequencing panel array for genes associated with hereditary neuromuscular disorders was used for analysis. The patients exhibited predominant muscle weakness. Electromyography revealed myopathic changes. The muscle biopsy showed myopathic features, such as increased fiber size variation, muscle fiber atrophy and regeneration, slight hyperplasia of the connective tissue, and disarray of the myofibrillar network. Two patients were confirmed to have mutations in the open reading frame of TCAP by next-generation sequencing. One patient had compound heterozygous mutations, and the other patient harbored a novel homozygous mutation. Western blotting analysis of the skeletal muscle lysate confirmed the absence of telethonin in the patients. We described two LGMD-R7 patients presenting a classical LGMD phenotype and a novel homozygous TCAP mutation. Our research expands the spectrum of LGMD-R7 due to TCAP mutations based on patients from a Chinese neuromuscular center.

Integrating 16S RRNA gene sequencing and metabolomics to evaluate the association between gut microbiota and serum metabolites in patients with myositis.

AIMS: Gut microbiota and metabolites have a profound impact on the maintenance of body health. In this study, we assessed the association between gut microbiota and serum metabolite changes in myositis using 16S rRNA gene sequencing and metabolomics to provide new ideas for screening and treating myositis. METHODS AND RESULTS: Blood and faecal samples were collected from 20 myositis patients and 20 healthy control subjects. Then, 16S rRNA gene sequencing, enzyme-linked immunosorbent assays and untargeted metabolomics study were performed to evaluate the relationship between gut microbiota and serum metabolites in patients with myositis. Compared to healthy control subjects, the blood samples from the patients with myositis had elevated levels of interleukin-4 (IL-4), tumour necrosis factor-α (TNF-α), and malondialdehyde (MDA) and decreased superoxide dismutase (SOD) levels. The increase in Bacteroidota (including Bacteroides and Parabacteroides, but not Prevotella) and the decrease in Firmicutes in the patients were accompanied by functional changes in amino acid and lipid metabolism. The gut microbiota (Bacteroides and Parabacteroides) were negatively correlated with the differential serum metabolites (glutamate and taurine). The differential serum metabolites (glutamate, pyrrolidonecarboxylic acid, and taurine) were also correlated with inflammatory factors (IL-4 and TNF-α) and oxidative stress indexes (MDA and SOD). CONCLUSION: Dysbiosis of gut microbiota in patients with myositis was accompanied by changes in inflammatory factors, oxidative stress indexes, and small molecule metabolites in serum. SIGNIFICANCE AND IMPACT OF STUDY: Blood and faecal biomarkers could be used for screening myositis.

Expanding the clinicopathological-genetic spectrum of GNE myopathy by a Chinese neuromuscular centre.

GNE myopathy is a heterogeneous group of ultrarare neuromuscular disorders caused by mutations in the GNE gene. An estimated prevalence of 1~21/1,000,000 leads to a deficiency of data and a lack of availability of samples to conduct clinical research on this neuromuscular disorder. Although GNE, which is the mutated gene responsible for the disease, is well known as the key enzyme in the biosynthesis pathway of sialic acid, the clinicopathological-genetic spectrum of GNE mutant patients is still unclear and expanding. This study presents ten unrelated patients with GNE myopathy, discovering five novel missense mutations. Clinical, electrophysiological, imaging, pathological and genetic data are presented in a retrospective manner. Interestingly, several patients in the cohort were found to have peripheral neuropathy and inflammatory cell infiltration in muscle biopsies, which have seldom been reported. This study, conducted by a neuromuscular centre in China, is the first attempt to highlight these abnormal clinicopathological features and associate them with genetic mutations in GNE myopathy.

Clinicopathological features of titinopathy from a Chinese neuromuscular center.

Titin, one of the largest proteins in humans, is a major component of muscle sarcomeres. Pathogenic variants in the titin gene (TTN) have been reported to cause a range of skeletal muscle diseases, collectively known as titinopathy. Titinopathy is a heterogeneous group of disabling diseases characterized by muscle weakness. In our study, we aimed to establish the clinicopathological-genetic spectrum of titinopathy from a single neuromuscular center. Three patients were diagnosed as having definite titinopathy, and additional three patients were diagnosed as having possible titinopathy according to the diagnostic criteria. All the patients showed initial symptoms from age one to 40 years. Physical examination revealed that five patients had muscle weakness, and that one patient experienced behavioral changes. Muscle biopsy specimens obtained from all six patients demonstrated multiple myopathological changes, including increased fiber size variation, muscle fiber hypertrophy or atrophy, formation of centralized cell nuclei, necklace cytoplasmic bodies, and formation of rimmed vacuoles and cores. Genetic testing revealed 11 different TTN alterations, including missense (6/11), nonsense (2/11), frameshift (2/11), and splicing (1/11) mutations. Our study provides further evidence that TTN mutations are more likely to be responsible for an increasing proportion of various myopathies, such as hereditary myopathy with early respiratory failure (HMERF), core myopathy, and distal myopathy with rimmed vacuoles, than currently recognized mutations. Our findings expand the clinical, pathohistological and genetic spectrum of titinopathy.

Investigation of adult-onset multiple acyl-CoA dehydrogenase deficiency associated with peripheral neuropathy.

Multiple Acyl-CoA dehydrogenase deficiency (MADD), one of the most common lipid storage myopathies (LSMs), is a heterogeneous inherited muscular disorder that is pathologically characterized by numerous lipid droplets in muscle fibers due to lipid metabolism disturbance. MADD exhibits a wide range of clinical features, including skeletal muscle weakness and multisystem dysfunctions. However, MADD, as well as other types of LSM, associated with peripheral neuropathy has rarely been reported during the past four decades. Here, we present four Chinese patients affected by MADD with peripheral neuropathy in our neuromuscular center. Clinically, these four patients showed skeletal muscle weakness and prominent paresthesia. Muscle biopsy detected characteristic myopathological patterns of LSM, such as obvious lipid droplets in muscle fibers. Sural nerve biopsy revealed a severe reduction in number of myelinated nerve fibers, which is a typical neuropathological pattern of peripheral neuropathy. Causative ETFDH mutations were found in all four cases. The skeletal muscle weakness was rapidly improved after some treatments while paresthesia showed unsatisfactory improvement. The features of previously reported patients of this specific type are also summarized in this paper. We propose that MADD with peripheral neuropathy may be a new phenotypic subtype because the pathology and reaction to riboflavin treatment are different from those of traditional MADD, although further research on the precise pathogenesis and mechanisms is needed.

[Clinical, pathological and genetic studies of two cases of childhood-onset nemaline myopathy].

This article reports two cases of childhood-onset nemaline myopathy diagnosed by muscle pathology and genetic diagnosis. The two patients had onset in early childhood, with muscle weakness as the first manifestation, as well as long disease duration and slow progression. Gomori staining and hematoxylin-eosin staining showed red-stained rods in the sarcoplasmic cytoplasm and sarcolemma under a light microscope. Electron microscopy showed that the dense nemaline rods were located under the muscle fiber sarcolemma and parallel to the long axis of the muscle fibers, and some muscle fiber myofilaments were dissolved and necrotic. Gene testing found that one of the two patients had heterozygous mutation (c.1013A>C) in the ACTA1 gene, and the other had compound heterozygous mutation (c.18676C>T and c.9812C>A) in the NEB gene. The two mutations were more common in nemaline myopathy. Nemaline myopathy is a recessive or dominant inheritance myopathy, in which the nemaline rod in the cytoplasm of myocytes is a characteristic muscle pathological change. Pathological and genetic diagnosis is the gold standard for diagnosis of nemaline myopathy.

IFNA-AS1 regulates CD4+ T cell activation in myasthenia gravis though HLA-DRB1.

Abnormal CD4+T cell activation is known to play roles in the pathogenesis of myasthenia gravis (MG). However, little is known about the mechanisms underlying the roles of lncRNAs in regulating CD4+ T cell. In this study, we discovered that the lncRNA IFNG-AS1 is abnormally expressed in MG patients associated with quantitative myasthenia gravis (QMG) and the positive anti-AchR Ab levels patients. IFNG-AS1 influenced Th1/Treg cell proliferation and regulated the expression levels of their transcription factors in an experimental autoimmune myasthenia gravis (EAMG)model. IFNG-AS1 could reduce the expression of HLA-DRB and HLA-DOB and they had a negative correlation in MG. Furthermore IFNG-AS1 influenced the expression levels of CD40L and CD4+ T cells activation in MG patient partly depend on effecting the HLA-DRB1 expression. It suggests that IFNG-AS1 may be involved in CD4+T cell-mediated immune responses in MG.

Dermatomyositis, polymyositis and immune-mediated necrotising myopathies.

Dermatomyositis, polymyositis and immune-mediated necrotising myopathy are major forms of idiopathic inflammatory myopathy. We review here recent developments in understanding the pathology and pathogenesis of these diseases, and characterisation of autoantibody biomarkers. Dermatomyositis is traditionally considered to be due to a complement-mediated microangiopathy but the factors responsible for complement activation remain uncertain. Recent studies have emphasised the importance of the type I interferon pathway in the pathogenesis of the disease and have identified autoantibodies with specificities for different clinical subgroups of patients. Polymyositis is characterised by a cytotoxic T cell response targeting as yet unidentified muscle antigens presented by MHC Class I molecules, and can occur in isolation but is more often part of a multi-systemic overlap syndrome. The immune-mediated necrotising myopathies are heterogeneous and are distinguished from polymyositis by the sparseness of inflammatory infiltrates and recognition of an association with specific autoantibodies such as anti-SRP and anti-HMGCR in many cases. This article is part of a Special Issue entitled: Neuromuscular Diseases: Pathology and Molecular Pathogenesis.

MiR-15a contributes abnormal immune response in myasthenia gravis by targeting CXCL10.

MiR-15a is likely to be associated with autoimmunity. Here, we aimed to examine the expression of miR-15 cluster in PBMCs from myasthenia gravis (MG) patients and investigate the potential roles of miR-15a in MG. We found that the expression of all miR-15 cluster was decreased in MG, furthermore, miR-15a levels in ocular MG (oMG) were much lower, while CXCL10 production was increased in MG. We display that CXCL10 was a functional target gene of miR-15a in MG. Increasing miR-15a expression could reduce CXCL10 expression and alleviate the abnormal T cells activation in immune response, while decreasing miR-15a expression could activate immune response abnormally. Moreover, miR-15a expression was significantly decreased after stimulation, and prednisone treatment could upregulate miR-15a expression in steroid-responsive MG patients. Take together, our data suggest that decreased miR-15a expression facilitates proinflammatory cytokines production and contributes to immune response at least in part via regulating CXCL10 expression in MG.

Normal and aberrant splicing of LMNA.

The LMNA gene gives rise to at least three isoforms (lamin A, C, lamin AΔ10) as a result of normal alternative splicing, regulated by cis- and trans-acting regulatory factors, as well as the 5' and 3' untranslated regions of the gene. The two main isoforms, lamin A and C, are constitutive components of the fibrous nuclear lamina and have diverse physiological roles, ranging from mechanical nuclear membrane maintenance to gene regulation. The clinical spectrum of diseases (called 'laminopathies') caused by LMNA mutations is broad, including at least eight well-characterised phenotypes, some of which are confined to the skeletal muscles or skin, while others are multisystemic. This review discusses the different alternatively spliced isoforms of LMNA and the regulation of LMNA splicing, as well as the subgroup of mutations that affect splicing of LMNA pre-mRNA, and also seeks to bridge the mis-splicing of LMNA at transcript level and the resulting clinical phenotypes. Finally, we discuss the manipulation of LMNA splicing by splice-switching antisense oligonucleotides and its therapeutic potential for the treatment of some laminopathies.

Biomarker studies in multiple sclerosis: from proteins to noncoding RNAs.

Multiple sclerosis (MS) is a neuroimmunological disorder characterized by central nervous system demyelination, axonal injury and loss. Considering the complexity of its aetiopathogenesis, early diagnosis of MS and individualized management are challenging in clinical practice. As the pathophysiologic and pharmacological indicators, studies on biomarkers in MS are useful for early prediction and diagnosis, monitoring of disease activity and predicting treatment response. In this review, we will summarize recent development of biomarker studies in MS from protein molecules to noncoding RNAs.

Twinkle mutations in two Chinese families with autosomal dominant progressive external ophthalmoplegia.

Autosomal dominant progressive external ophthalmoplegia (adPEO) is a common adult onset mitochondrial disease caused by mutations in nuclear DNA (nDNA). Twinkle is one of the nuclear genes associated with adPEO. Clinical, histochemical, and molecular genetics findings of 6 patients from two Chinese families with adPEO were reported. Two point mutations (c.1423G>C, p.A475P and c.1061G>C, p.R354P) of Twinkle gene have been found. Multiple mtDNA deletions were also detected in patient's muscle and fibroblasts. This study confirms two mutations in Chinese adPEO families, which were first reported in the Chinese population.

Comparative effectiveness and safety of intravenous methylprednisolone and tacrolimus monotherapy in ocular myasthenia gravis with unsatisfactory prednisone responses: a retrospective study.

BACKGROUND: Oral prednisone has been recognized as the first-line therapy for the treatment of ocular myasthenia gravis (OMG). However, its long-term use is complicated by numerous adverse effects and is ineffective for some OMG patients in reaching remission. This study aimed to evaluate the effectiveness and safety of intravenous methylprednisolone (IVMP) and tacrolimus monotherapy for OMG patients with unsatisfactory responses to conventional prednisone therapy. METHODS: We retrospectively reviewed 57 OMG patients who had not achieved satisfactory improvement after prednisone therapy and thereby received IVMP or tacrolimus monotherapy for at least 6 months. Ocular symptoms were evaluated by the ocular-quantitative MG (QMG) score at each time point. A ≥ 2-point fall in ocular QMG score was defined as the cut-off point to indicate clinical improvement. Logistic regression analysis was performed to identify factors associated with the efficacy of IVMP at discharge. Adverse events were recorded. RESULTS: Both IVMP and tacrolimus monotherapy demonstrated significant clinical efficacy, with no statistical differences observed at the study endpoint. The proportions of patients who reached the cut-off point for efficacy evaluation were higher in the IVMP group than in the tacrolimus group (1, 3, and 6 months: 51.7% (15/29) vs 12.0% (3/25), p = 0.002; 69.0% (20/29) vs 40.0% (10/25), p = 0.033; 69.0% (20/29) vs 46.4% (13/28), p = 0.085, respectively). Multivariate logistics analysis showed that high ocular QMG scores at baseline indicated favourable responses to IVMP treatment (OR = 1.781; 95% CI 1.066-2.975; p = 0.028). All the adverse events were transient and tolerable. CONCLUSION: Our findings suggest that both IVMP and tacrolimus monotherapy hold promise as viable treatment options for OMG patients with unsatisfactory responses to oral prednisone. The study supports the safety and effectiveness of both therapies, with IVMP exhibiting faster improvement and favourable efficacy in patients with high ocular QMG scores.

Primary over-expression of AßPP in muscle does not lead to the development of inclusion body myositis in a new lineage of the MCK-AßPP transgenic mouse.

The aim of this study is to determine whether primary over-expression of AßPP in skeletal muscle results in the development of features of inclusion body myositis (IBM) in a new lineage of the MCK-AßPP transgenic mouse. Quantitative histological, immunohistochemical and western blotting studies were performed on muscles from 3 to 18 month old transgenic and wild-type C57BL6/SJL mice. Electron microscopy was also performed on muscle sections from selected animals. Although western blotting confirmed that there was over-expression of full length AßPP in transgenic mouse muscles, deposition of amyloid-ß and fibrillar amyloid could not be demonstrated histochemically or with electron microscopy. Additionally, other changes typical of IBM such as rimmed vacuoles, cytochrome C oxidase-deficient fibres, upregulation of MHC antigens, lymphocytic inflammatory infiltration and T cell fibre invasion were absent. The most prominent finding in both transgenic and wild-type animals was the presence of tubular aggregates which was age-related and largely restricted to male animals. Expression of full length AßPP in this MCK-AßPP mouse lineage did not reach the levels required for immunodetection or deposition of amyloid-ß as in the original transgenic strains, and was not associated with the development of pathological features of IBM. These negative results emphasise the potential pitfalls of re-deriving transgenic mouse strains in different laboratories.

Clinical Reasoning: A 74-Year-Old Woman Presenting With Monocular Ptosis and Binocular Diplopia.

A 74-year-old woman presented with acute-onset right ptosis and binocular diplopia. CT scan showed low-density lesions in the bilateral basal ganglia and adjacent to lateral ventricles. Intracranial aneurysm was not detected. This case highlights the importance of neurologic localization of ophthalmoplegia based on physical examination and the microanatomy of the oculomotor nerve.

Adult-Onset Neuronal Intranuclear Inclusion Disease with Mitochondrial Encephalomyopathy, Lactic Acidosis, and Stroke-Like (MELAS-like) Episode: A Case Report and Review of Literature.

Neuronal intranuclear inclusion disease (NIID) is a rare neurodegenerative disease with highly heterogeneous manifestations. Curvilinear hyperintensity along the corticomedullary junction on diffusion-weighted images (DWI) is a vital clue for diagnosing NIID. DWI hyperintensity tends to show an anterior-to-posterior propagation pattern as the disease progresses. The rare cases of its disappearance may lead to misdiagnosis. Here, we reported a NIID patient with mitochondrial encephalomyopathy, lactic acidosis and stroke-like (MELAS-like) episode, and reversible DWI hyperintensities. A review of the literature on NIID with MELAS-like episodes was conducted. A 69-year-old woman stated to our clinics for recurrent nausea/vomiting, mixed aphasia, altered mental status, and muscle weakness for 2 weeks. Neurological examination showed impaired mental attention and reaction capacity, miosis, mixed aphasia, decreased muscle strength in limbs, and reduced tendon reflex. Blood tests were unremarkable. The serological examination was positive for antibody against dipeptidyl-peptidase-like protein 6 (DPPX) (1:32). Brain magnetic resonance imaging (MRI) revealed hyperintensities in the left temporal occipitoparietal lobe on DWI and correspondingly elevated lactate peak in the identified restricted diffusion area on magnetic resonance spectroscopy, mimicking the image of MELAS. Skin biopsy and genetic testing confirmed the diagnosis of NIID. Pulse intravenous methylprednisolone and oral prednisolone were administered, ameliorating her condition with improved neuroimages. This case highlights the importance of distinguishing NIID and MELAS, and reversible DWI hyperintensities can be seen in NIID.

Expanding the clinicopathological-genetic spectrum of glycogen storage disease type IXd by a Chinese neuromuscular center.

Background: Glycogen storage disease (GSDs) is characterized by abnormally inherited glycogen metabolism. GSD IXd, which is caused by mutations in the PHKA1 gene, is an X-linked rare disease with mild myopathic symptoms. To date, only 13 patients with GSD IXd have been reported. In this study, we aimed to expand the clinicopathological-genetic spectrum of GSD IXd at a neuromuscular center in China. Methods: Data on patients diagnosed with GSD IXd at our neuromuscular center were collected retrospectively. Clinical features, electrophysiology, muscle pathology, and genetic information were analyzed. Results: Between 2015 and 2021, three patients were diagnosed with GSD IXd based on clinical manifestations, pathological findings, and genetic testing. One patient presented with mitochondrial myopathy. All patients exhibited muscle weakness and elevated levels of creatine kinase. Electromyography-detected myopathic changes were found in two patients, whereas one patient refused to undergo this examination. Pathological examinations in all patients revealed subsarcolemmal accumulation of glycogen under PAS staining. All patients had mutations in the PHKA1 gene and the patient with mitochondrial myopathy also had a mutation in the MT-TL1 gene. Conclusion: Our study expands the clinicogenotype and phenotype of GSD IXd in a Chinese population. Our study also expands the known mutation spectrum for GSD IXd, contributing to a better characterization and understanding of this ultrarare neuromuscular disorder.

CASQ1-related myopathy: The first report from China and the literature review.

Calsequestrin 1 (CASQ1) is the most crucial Ca2+ binding protein localized in the sarcoplasmic reticulum (SR) of skeletal muscle. With high capacity and low affinity for Ca2+, CASQ1 plays a significant role in maintaining a large amount of Ca2+ necessary for muscle contraction. However, only five mutations in CASQ1 have been identified to date. Here, we report a 42-year-old Chinese female patient who presented with a 12 years history of slowly progressive upper limb weakness, predominantly affecting distal muscles, which was uncommon comparing to other CASQ1-related patients. Next-generation sequencing (NGS) analysis revealed a novel heterozygous mutation (c.766G > A, p.Val256Met) in CASQ1. Functional studies confirmed the likely pathogenicity of this variant. Muscle histopathology revealed rare optically empty vacuoles in myofibers and atypical eosinophilic granules in the cytoplasm, which has not been observed before. We also performed a literature review on all the pathogenic mutations in CASQ1 and summarized their genetic and clinical characteristics. This is the first report on CASQ1-related myopathy from China, further expanding the mutation spectrum of CASQ1 gene and provides new insights into the function of CASQ1.