muscle-visualization-evaluation-methods-for-immune-checkpoint

Muscle Visualization and Evaluation Methods for Immune Checkpoint Inhibitor-Related Myositis

Immune checkpoint inhibitors (ICIs) have fundamentally transformed the landscape of cancer therapy, yet their administration frequently correlates with ...

Fudan University

National Center for Neurological Disorders (NCND)

Limb girdle muscular dystrophy type R25 (LGMDR25) is a rare genetic disorder due to loss-of-function mutations in BVES, characterized by progressive proximal lower limb weakness and atrioventricular block. Here we report a young Chinese man with LGMDR25 who presented with asymmetrical lower limb weakness, myalgia, palpitations and dyspnea on exertion. Muscle imaging demonstrated fatty infiltration of the long head of biceps femoris, adductor magnus, gastrocnemius and soleus, and myoedema of semitendinosus and quadriceps, sparing rectus femoris. ECG showed only mild sinus tachycardia but pulmonary function test suggested prominent respiratory muscle weakness. Our report expands the phenotypical spectrum and indicates the importance of monitoring respiratory function in LGMDR25 patients.

Early respiratory muscle involvement in LGMDR25: a case report.

Oculopharyngodistal myopathy (OPDM) is a late-onset degenerative muscle disorder characterized by ptosis and weakening of the facial, pharyngeal, and distal limb muscles. Our study reprogrammed human-induced pluripotent stem cells (iPSC) from the peripheral blood mononuclear cells (PBMCs) of a patient with a CGG repeat expansion in the 5'UTR of GIPC1 gene that co-segregated with the disease. The generated iPSCs express the pluripotent cell markers with no mycoplasma contamination. Besides, it showed normal karyotypes and the capacity to differentiate into three germ layers. We also identified that it had the same specific mutation as the patient did.

Human-induced pluripotent stem cell line (FDHSi001-A) derived from a patient with a CGG repeat expansion in the 5'UTR of GIPC1.

Surveys and retrospective studies have revealed considerable delays in diagnosing late-onset Pompe disease (LOPD) in China, where the contributing factors remain poorly represented. Our study analyzed the diagnostic journey of 34 LOPD patients seen at our neuromuscular clinic from 2005 to 2022. We defined diagnostic delay as the time from the onset of the first relevant symptoms and laboratory findings suggestive of LOPD to the eventual diagnosis, and we constructed a correlation matrix to assess relationships among these variables. The cohort consisted of 34 patients with an equal male-to-female ratio, and the mean age at diagnosis was 27.68 ± 10.03 years. We found the median diagnostic delay to be 5 years, with a range of 0.3 to 20 years, with 97.1% having been misdiagnosed previously, most commonly with "Type II Respiratory insufficiency" (36.7%). Notably, patients at earlier onset (mean age, 18.19 years vs. 31 years;  < 0.005) tended to have higher creatine kinase (CK) levels. Furthermore, 92.6% reported difficulty in sitting up from a supine position since childhood. Our research emphasizes the role of early indicators like dyspnea and difficulty performing sit-ups in adolescents for timely LOPD diagnosis and treatment initiation. The importance of early high-risk screening using dried blood spot testing cannot be overstated.

Diagnostic delay in late-onset Pompe disease among Chinese patients: A retrospective study.

Spinal muscular atrophy (SMA) is an autosomal recessive neuromuscular disorder primarily caused by the deletion or mutation of the survival motor neuron 1 (SMN1) gene. This study assesses the diagnostic potential of long-read sequencing (LRS) in three patients with SMA. For Patient 1, who has a heterozygous SMN1 deletion, LRS unveiled a missense mutation in SMN1 exon 5. In Patient 2, an Alu/Alu-mediated rearrangement covering the SMN1 promoter and exon 1 was identified through a blend of multiplex ligation-dependent probe amplification, LRS, and PCR across the breakpoint. The third patient, born to a consanguineous family, bore four copies of hybrid SMN genes. LRS determined the genomic structures, indicating two distinct hybrids of SMN2 exon 7 and SMN1 exon 8. However, a discrepancy was found between the SMN1/SMN2 ratio interpretations by LRS (0:2) and multiplex ligation-dependent probe amplification (0:4), which suggested a limitation of LRS in SMA diagnosis. In conclusion, this newly adapted long PCR-based third-generation sequencing introduces an additional avenue for SMA diagnosis.

Diagnosis of Challenging Spinal Muscular Atrophy Cases with Long-Read Sequencing.

GNE myopathy is a rare autosomal recessive disorder caused by pathogenic variants in the GNE gene, which is essential for the sialic acid biosynthesis pathway. Although over 300 GNE variants have been reported, some patients remain undiagnosed with monoallelic pathogenic variants. This study aims to analyze the entire GNE genomic region to identify novel pathogenic variants.

Pseudoexon activation by deep intronic variation in GNE myopathy with thrombocytopenia.

5q spinal muscular atrophy (SMA) is a progressive autosomal recessive motor neuron disease.

Long-term impact of nusinersen on motor and electrophysiological outcomes in adolescent and adult spinal muscular atrophy: insights from a multicenter retrospective study.

Late-onset Pompe disease (LOPD) is caused by a genetic deficiency of the lysosomal enzyme acid alpha-glucosidase (GAA), leading to progressive limb-girdle weakness and respiratory impairment. The insidious onset of non-specific early symptoms often prohibits timely diagnosis. This study aimed to validate the high-risk screening criteria for LOPD in the Chinese population. A total of 726 patients were included, including 96 patients under 14 years of age. Dried blood spots (DBS) and tandem mass spectrometry (MS/MS) were employed to evaluate serum GAA activity. Forty-four patients exhibited a decreased GAA activity, 16 (2.2%) of which were confirmed as LOPD by genetic testing. Three previously unreported GAA mutations were also identified. The median diagnostic delay was shortened to 3 years, which excelled the previous retrospective studies. At diagnosis, most patients exhibited impaired respiratory function and/or limb-girdle weakness. Elevated serum creatine kinase (CK) levels were more frequently observed in patients who manifested before age 16. Overall, high-risk screening is a feasible and efficient method to identify LOPD patients at an early stage. Patients over 1 year of age with either weakness in axial and/or proximal limb muscles, or unexplained respiratory distress shall be subject to GAA enzymatic test, while CK levels above 2 times the upper normal limit shall be an additional criterion for patients under 16. This modified high-risk screening criteria for LOPD requires further validation in larger Chinese cohorts.

High-risk screening for late-onset Pompe disease in China: An expanded multicenter study.

GlcNAc2-epimerase myopathy is a rare autosomal recessive myopathy characterized by distal involvement in the lower extremities. Our study reprogrammed human-induced pluripotent stem cells from peripheral blood mononuclear cells of a patient with GNE gene deep intronic variant c.862 + 870C>T and c.478C>T compound heterozygous mutations that co-segregated with the disease. The generated iPSCs express pluripotent cell markers with no mycoplasma contamination. Additionally, these iPSCs demonstrated pluripotency, the capacity to differentiate into the three germ layers, and maintained normal karyotypes. Importantly, we identified that these iPSCs possess the same specific mutations as the patient, making them a robust model for studying GNE myopathy and developing potential therapeutic interventions.

Human induced pluripotent stem cell line (FDHSi005-A) derived from a patient with a deep intronic variant in the GNE gene.

GlcNAc2-epimerase (GNE) myopathy is a rare autosomal recessive disorder caused by pathogenic variants in the  gene, which is essential for the sialic acid biosynthesis pathway.

Novel variants and genotype-phenotype correlation in a multicentre cohort of GNE myopathy in China.

Facioscapulohumeral muscular dystrophy (FSHD) is caused by pleiotropic contractions of the D4Z4 repeat array on chromosome 4q35 (FSHD1) or by mutations in repressive chromatin regulators of the D4Z4 loci (FSHD2), both resulting in epigenetic dysregulation at the D4Z4 array. DNA methylation of the D4Z4 repeat array has been proposed for diagnosis and prognosis of FSHD disease severity; however, further validation in larger populations is needed. Two hundred forty-seven clinically suspected FSHD cases were retrospectively analyzed with D4Z4 analysis by optical genome mapping or molecular combing and tested the DNA methylation levels for 75 patients and 49 healthy controls. A D4Z4 repeat length-dependent nonlinear increase was observed in both distal and global D4Z4 methylation levels. Distal D4Z4 methylation levels identified patients with FSHD1 with a sensitivity of 100% and a specificity of 97.96% at a cutoff value of 39.66% compared with controls. Distal FSHD1-like hypomethylation was also observed in one subject carrying a special D4Z4 rearrangement, resulting in a proximal contracted array. Clinically, distal methylation levels demonstrated a strong correlation with the age-corrected clinical severity score and onset age. Mediation analysis revealed that the influence of distal methylation on age-corrected clinical severity score was partially mediated by onset age. This study further confirms the distal 4qA D4Z4 methylation analysis as a valuable complement for differential diagnosis in patients with suspected FSHD, including those with complex structural variants.

4qA D4Z4 Methylation Test as a Valuable Complement for Differential Diagnosis in Patients with a Facioscapulohumeral Muscular Dystrophy-Like Phenotype.

Antibodies to 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCR) form a newly identified distinct serological marker for necrotizing autoimmune myopathy. Although anti-HMGCR myopathy is currently classified into polymyositis, skin involvement has been reported, with its characteristics only vaguely described. We retrospectively examined the clinical and histological features of non-dermatomyositis-like persistent exanthema in five anti-HMGCR myopathy patients followed up in the neurology and dermatology clinic of Huashan Hospital between December 2020 and September 2024. The exanthema presented as persistent violaceous or erythematous plaques, asymptomatic or itching, mainly distributed on the trunk, whereas dermatomyositis-specific lesions such as Gottron's sign and papules, heliotrope rash, V or shawl signs, and nailfold telangiectasia were all absent. Skin rash in 80% of patients (4/5) appeared earlier than muscle symptoms such as fatigue, proximal limb weakness, and hyperCKemia, with the median advanced time of 3 years (8 months to 7 years). Biopsies revealed scant interface dermatitis, interstitial mucin, and perivascular lymphocytic infiltrate with occasionally plasma cells and/or neutrophils. Notably, the exanthema showed no response to topical or even systemic corticosteroid but relieved after systemic immunosuppressive therapy for myopathy, in accordance with the improvement of muscle symptoms and hyperCKemia. Dermatologists should be aware of this rare entity of "pseudo-dermatomyositis", carefully evaluate muscle syndromes and carry out further investigations, including muscle biopsy and serum anti-HMGCR antibodies assays if present.

Persistent exanthema mainly on the trunk with pathologically dermal interstitial mucin as anti-HMGCR myopathy-associated skin rash: Case series.

Aberrant inclusion of pseudoexons (PE) in mature mRNA is a rare splicing defect contributing to Duchenne muscular dystrophy (DMD) pathogenesis. In this study, we described two affected males from a Chinese family who presented with progressive muscle weakness, elevated creatine kinase (CK) levels, and dystrophic changes on muscle pathology. Whole-genome sequencing followed by linkage-based filtering identified a shared deep intronic variant in intron 47 of DMD gene (c.6913-4037T>G), which activated a cryptic splice site and resulted in the inclusion of a 72 bp PE between exons 47 and 48. Patient induced pluripotent stem cells (iPSCs)-derived myotubes from the patient confirmed the presence of this PE, with a significant reduction in dystrophin expression compared to controls. Quantitative PCR revealed that aberrant transcripts comprised ~89% of total DMD transcripts in myotubes and ~97% in muscle, correlating with near-complete loss of dystrophin. Functional assays further showed impaired myotube fusion and altered calcium signaling. This study underscores the diagnostic complexity of intronic DMD variants and provides evidence supporting the pathogenicity of c.6913-4037T>G.

Article	Year
Early respiratory muscle involvement in LGMDR25: a case report. Neuromuscular disorders : NMD\| PubMed ID: 35718670	2022
Human-induced pluripotent stem cell line (FDHSi001-A) derived from a patient with a CGG repeat expansion in the 5'UTR of GIPC1. Stem cell research\| PubMed ID: 36055118	2022
Diagnostic delay in late-onset Pompe disease among Chinese patients: A retrospective study. JIMD reports\| PubMed ID: 38186848	2024
Diagnosis of Challenging Spinal Muscular Atrophy Cases with Long-Read Sequencing. The Journal of molecular diagnostics : JMD\| PubMed ID: 38490302	2024
Pseudoexon activation by deep intronic variation in GNE myopathy with thrombocytopenia. Muscle & nerve\| PubMed ID: 38558464	2024
Long-term impact of nusinersen on motor and electrophysiological outcomes in adolescent and adult spinal muscular atrophy: insights from a multicenter retrospective study. Journal of neurology\| PubMed ID: 39030456	2024
High-risk screening for late-onset Pompe disease in China: An expanded multicenter study. Journal of inherited metabolic disease\| PubMed ID: 39227307	2025
Human induced pluripotent stem cell line (FDHSi005-A) derived from a patient with a deep intronic variant in the GNE gene. Stem cell research\| PubMed ID: 39303320	2024
Novel variants and genotype-phenotype correlation in a multicentre cohort of GNE myopathy in China. Journal of medical genetics\| PubMed ID: 39332896	2024
4qA D4Z4 Methylation Test as a Valuable Complement for Differential Diagnosis in Patients with a Facioscapulohumeral Muscular Dystrophy-Like Phenotype. The Journal of molecular diagnostics : JMD\| PubMed ID: 40113166	2025
Persistent exanthema mainly on the trunk with pathologically dermal interstitial mucin as anti-HMGCR myopathy-associated skin rash: Case series. The Journal of dermatology\| PubMed ID: 40152349	2025
Pseudoexon activating by a deep intronic variant and phenotype variation in a Chinese family with dystrophinopathy. Journal of human genetics\| PubMed ID: 40583054	2025

Nachuan Cheng

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