Congenital myasthenic syndromes in the Thai population: Clinical findings and novel mutations

Preimplantation genetic testing as a means of preventing hereditary congenital myasthenic syndrome caused by RAPSN

BACKGROUND

Congenital myasthenic syndrome is a heterogeneous group of inherited neuromuscular transmission disorders. Variants in RAPSN are a common cause of CMS, accounting for approximately 14%-27% of all CMS cases. Whether preimplantation genetic testing for monogenic disease (PGT-M) could be used to prevent the potential birth of CMS-affected children is unclear.

METHODS

Application of WES (whole-exome sequencing) for carrier testing and guidance for the PGT-M in the absence of a genetically characterized index patient as well as assisted reproductive technology were employed to prevent the occurrence of birth defects in subsequent pregnancy. The clinical phenotypes of stillborn fetuses were also assessed.

RESULTS

The family carried two likely pathogenic variants in RAPSN(NM_005055.5): c.133G>A (p.V45M) and c.280G>A (p.E94K). And the potential birth of CMS-affected child was successfully prevented, allowing the family to have offspring devoid of disease-associated variants and exhibiting a normal phenotype.

CONCLUSION

This report constitutes the first documented case of achieving a CMS-free offspring through PGT-M in a CMS-affected family. By broadening the known variant spectrum of RAPSN in the Chinese population, our findings underscore the feasibility and effectiveness of PGT-M for preventing CMS, offering valuable insights for similarly affected families.

Genetic and clinical evaluation of congenital myasthenic syndromes with long-term follow-up: experience of a tertiary center in Turkey

INTRODUCTION

Congenital myasthenic syndromes (CMS) are a heterogeneous group of genetic disorders affecting the safety factor which required for neuromuscular transmission. Here we reported our experience in children with CMS.

METHODS

We retrospectively collected the data of 18 patients with CMS who were examined in our outpatient clinic between January 2021 and January 2022. The diagnosis of CMS was based on the presence of clinical symptoms such as abnormal fatigability and weakness, absence of autoantibodies against acetylcholine receptor and muscle-specific kinase, electromyographic evidence of neuromuscular junction defect, molecular genetic confirmation, and response to treatment.

RESULTS

The most common mutations were in the acetylcholine receptor (CHRNE) gene (8/18) and choline acetyltransferase (ChAT) (2/18) gene. Despite targeted gene sequencing and whole exome sequencing (WES) were underwent, we couldn't detect a genetic mutation in three out of patients. The most commonly determined initial finding was eyelid ptosis, followed by fatigable weakness, and respiratory insufficiency. Although the most commonly used drug was pyridostigmine, we have experienced that caution should be exercised as it may worsen some types of CMS.

DISCUSSION

We reported in detail the phenotypic features of very rare gene mutations associated with CMS and our experience in the treatment of this disease. Although CMS are rare genetic disorder, the prognosis can be very promising with appropriate treatment in most CMS subtypes.

COLQ-related congenital myasthenic syndrome: An integrative view

Congenital myasthenic syndromes are inherited disorders caused by mutation in components of the neuromuscular junction and manifest early in life. Mutations in COLQ gene result in congenital myasthenic syndrome. Here, we present the analysis of data from 209 patients from 195 unrelated families highlighting genotype-phenotype correlation. In addition, we describe a COLQ homozygous variant a new patient and discuss it utilizing the Phyre2 and I-TASSER programs. Clinical, molecular genetics, imaging (MRI), and electrodiagnostic (EEG, EMG/NCS) evaluations were performed. Our data showed 89 pathogenic/likely pathogenic variants including 35 missenses, 21 indels, 14 nonsense, 14 splicing, and 5 large deletions variants. Eight common variants were responsible for 48.46% of those. Weakness in proximal muscles, hypotonia, and generalized weakness were detected in all individuals tested. Apart from the weakness, extensive clinical heterogeneity was noted among patients with COLQ-related patients based on their genotypes-those with variants affecting the splice site exhibited more severe clinical features while those with missense variants displayed milder phenotypes, suggesting the role of differential splice variants in multiple functions within the muscle. Analyses and descriptions of these COLQ variants may be helpful in clinical trial readiness and potential development of novel therapies in the setting of established structure-function relationships.

The clinical and molecular landscape of congenital myasthenic syndromes in Austria: a nationwide study

BACKGROUND

Congenital myasthenic syndromes (CMS) are a heterogeneous group of disorders caused by genetic defects resulting in impaired neuromuscular transmission. Although effective treatments are available, CMS is probably underdiagnosed, and systematic clinico-genetic investigations are warranted.

METHODS

We used a nationwide approach to collect Austrian patients with genetically confirmed CMS. We provide a clinical and molecular characterization of this cohort and aimed to ascertain the current frequency of CMS in Austria.

RESULTS

Twenty-eight cases with genetically confirmed CMS were identified, corresponding to an overall prevalence of 3.1 per million (95% CI 2.0-4.3) in Austria. The most frequent genetic etiology was CHRNE (n = 13), accounting for 46.4% of the cohort. Within this subgroup, the variant c.1327del, p.(Glu443Lysfs*64) was detected in nine individuals. Moreover, causative variants were found in DOK7 (n = 4), RAPSN (n = 3), COLQ (n = 2), GMPPB (n = 2), CHAT (n = 1), COL13A1 (n = 1), MUSK (n = 1) and AGRN (n = 1). Clinical onset within the first year of life was reported in one half of the patients. Across all subtypes, the most common symptoms were ptosis (85.7%), lower limb (67.9%), upper limb (60.7%) and facial weakness (60.7%). The majority of patients (96.4%) received specific treatment, including acetylcholinesterase inhibitors in 20, adrenergic agonists in 11 and 3,4-diaminopyridine in nine patients.

CONCLUSIONS

Our study presents the first systematic characterization of individuals with CMS in Austria, providing prevalence estimates and genotype-phenotype correlations that may help to improve the diagnostic approach and patient management.

Pharmacological Treatments for Congenital Myasthenic Syndromes Caused by COLQ Mutations

BACKGROUND

Congenital myasthenic syndromes (CMS) refer to a series of inherited disorders caused by defects in various proteins. Mutation in the collagen-like tail subunit of asymmetric acetylcholinesterase (COLQ) is the second-most common cause of CMS. However, data on pharmacological treatments are limited.

OBJECTIVE

In this study, we reviewed related reports to determine the most appropriate pharmacological strategy for CMS caused by COLQ mutations. A literature review and meta-analysis were also performed. PubMed, MEDLINE, Web of Science, and Cochrane Library databases were searched to identify studies published in English before July 22, 2022.

RESULTS

A total of 42 studies including 164 patients with CMS due to 72 different COLQ mutations were selected for evaluation. Most studies were case reports, and none were randomized clinical trials. Our meta-analysis revealed evidence that β-adrenergic agonists, including salbutamol and ephedrine, can be used as first-line pharmacological treatments for CMS patients with COLQ mutations, as 98.7% of patients (74/75) treated with β-adrenergic agonists showed positive effects. In addition, AChEIs should be avoided in CMS patients with COLQ mutations, as 90.5% (105/116) of patients treated with AChEIs showed either no or negative effects.

CONCLUSION

(1) β-adrenergic agonist therapy is the first pharmacological strategy for treating CMS with COLQ mutations. (2) AChEIs should be avoided in patients with CMS with COLQ mutations.

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.