Congenital myasthenic syndrome due to mutation in CHRNE gene with clinical worsening and thymic hyperplasia attributed to association with autoimmune-myasthenia gravis

Phenotypic variability in congenital myasthenic syndrome with GFPT1 mutation

BACKGROUND

Congenital myasthenic syndrome (CMS) is phenotypically and genetically different from myasthenia gravis. CMS can present in adolescents and can be treatable. Genetic testing is helpful in diagnosis, and guides therapy, alleviating the need of muscle biopsy. Also, Genetic diagnosis allows a diagnosis of certainty, especially if there is any doubt about a muscular pathology Henceforth, it is an important differential in those presenting with fixed or fluctuating weakness.

METHOD

Herein, we report two adolescent females with positive Glutamine-fructose-6-phosphate transaminase1( GFPT)mutation(c.322G > A p.Arg111His) with different phenotypic features. One of them presented with dysmorphic features, hyperextensible joints, features suggestive of metabolic myopathy on muscle biopsy and a strongly positive acetylcholine receptor (AChR) antibodies in serum. The second case presented with clinical features typical of congenital limb girdle myasthenic syndrome.

CONCLUSION

Our case had limb girdle weakness, dysmorphic features, uniquely positive AChR antibody, mitochondrial pathology on muscle biopsy and positive GFPT1 mutation. This phenotype has not been reported previously. Given the condition being potentially treatable, GFPT1 mutation subtype of CMS should be considered in differential diagnosis of limb girdle weakness phenotype even in the absence of family history.

Congenital myasthenic syndromes by Epsilon subunit mutations: Phenotypic profiles of 17 Algerian families

BACKGROUND

Congenital myasthenic syndromes (CMS) are a heterogeneous group of rare genetic disorders. The acetyl choline receptor contains five subunits, with a predominance of mutations affecting the epsilon subunit gene called cholinergic receptor nicotinic epsilon (CHRNE) gene.

OBJECTIVE

To study the clinical phenotype of 17 families with CHRNE gene mutations.

METHODS

We report a series of 17 families with 22 affected patients carrying different mutations encoding CHRNE proteins.

RESULTS

We studied their clinical and biological phenotypes, as well as their evolutionary profile and their response to the different therapies proposed. A phenotypic comparison was made between the families carrying the founding Maghrebian mutation and the other mutations found in this series.

CONCLUSION

The CHRNE gene mutations are the most frequent ones in CMS. The phenotypes reported in this study are heterogeneous, and can depend on the causative mutation.

CHRNE-related congenital myasthenic syndrome in Iran: Clinical and molecular insights

Variants in the CHRNE gene can lead to a condition called congenital myasthenic syndrome (CMS), which affects the neuromuscular junction (NMJ). CHRNE mutations are the most common cause of CMS. Seventy-seven patients with a possible diagnosis of CMS were referred to the neuromuscular clinic of Shariati Hospital affiliated with the Tehran University of Medical Sciences. We performed whole-exome sequencing (WES) to determine the underlying defect in a group of individuals with a possible diagnosis of CMS. Clinical features and morphological and molecular data on 33 patients with mutations in CHRNE were described. Age of onset, age at diagnosis, consanguinity, family history, motor milestone delay, ophthalmoparesis, generalized fatigue, dysphagia, neurophysiologic findings, and response to treatment of the patients were assessed. Nineteen CHRNE variants including 10 novel ones were identified. The most common mutations were c.1327del; (p.Glu443LysfsTer64) in four different families and c.1252-1267dup; (p.Cys423SerfsTer38) in three families. Clinical onset was mostly at birth or under one year with bilateral fatigable ptosis, ophthalmoplegia, bulbar weakness, and proximal muscle weakness. All patients were treated with pyridostigmine ± salbutamol, which resulted in improvement of motor function, dysphagia, and breathing.

Congenital Myasthenic Syndrome associated with acetylcholine receptor deficiency: case report and review of the literature

INTRODUCTION

Congenital Myasthenic Syndromes are a diverse group of conditions with a broad array of genetic underpinnings and phenotypic presentations. Acetylcholine receptor deficiency is one form that usually involves pathogenic variants in the Cholinergic Receptor Nicotinic Epsilon Subunit (CHRNE) gene encoding the ɛ-subunit of the acetylcholine receptor.

METHODS

We report a case of a 4-year-old male with suspected Congenital Myasthenic Syndrome with Acetylcholine Receptor Deficiency who presented with ocular symptoms and generalized muscle weakness. We additionally summarize published findings regarding the genetic, phenotypic, and clinical considerations of Congenital Myasthenic Syndrome with Acetylcholine Receptor Deficiency.

RESULTS

Exome sequencing revealed biallelic variants in CHRNE gene with a pathogenic frameshift variant and a variant of uncertain significance. After suboptimal response to pyridostigmine and albuterol, the patient experienced benefit with 3,4-DAP. The most commonly reported clinical characteristics in the literature are ptosis, muscle fatigability or weakness, and ophthalmoplegia.

CONCLUSION

We present the case of a patient with biallelic variants in CHRNE gene including a variant of uncertain significance. Evaluation of variants of this gene, including the variant of uncertain significance identified in this case report, through further cases and studies may improve our understanding of Congenital Myasthenic Syndrome with Acetylcholine Receptor deficiency.

Innovative Therapeutic Approaches in Congenital Myasthenic Syndromes

Background and Objectives

To provide real-word clinical follow-up data on patients carrying variations of congenital myasthenic syndromes (CMS) and who respond to some innovative drugs.

Methods

Patients recruited from the Neurology Department of the Mustapha Bacha university hospital in Algiers. Treated with innovative drugs, they were monitored and their clinical progress was evaluated on the basis of clinical arguments suggestive of CMSs, but also para clinical arguments (electromyography and genetic study).

Results

Six patients carrying different mutations in different genes of CMSs were studied. They had different pathophysiologic profiles (slow or fast channel syndromes, low expressor of receptor). Their therapeutic management was based on innovative drugs, normally indicated in other, non-neurological pathologies. Their outcome was toward a clear clinical improvement.

Discussion

This work relates the interest of proposing treatments (outside of Pyridostigmine) in the management of CMSs. These therapies can greatly modify the prognosis of patients suffering from this orphan disease.

Classification of Evidence

This study provides Class IV evidence that for patients with congenital myasthenic syndromes, some innovative treatments are effective.

[Congenital myasthenic syndromes with kinetic abnormalities of the acetylcholine receptor]

Congenital myasthenic syndromes (CMS) are genetically and phenotypically very heterogeneous conditions resulting in a defect in the neuromuscular transmission. Post-synaptic forms are the most frequent CMSs, and acetyl choline receptor (low expressor) deficiency is the most commonly involved pathophysiological mechanism. CMS with kinetic abnormalities of the acetylcholine receptor (AChr) are much rarer and can give rise to potentially life-threatening phenotypes. Among them, two types have been described: the slow channel syndrome (SCS) and the fast channel syndrome (FCS). Diagnosis and therapeutic management of such entities are specific to each type. In this work, we will illustrate the phenotypic aspects of CMS with kinetic abnormalities of the AChR by a narrative review of three Algerian families.

Oculopharyngeal muscular dystrophy coexisting with myasthenia gravis

Oculopharyngeal muscular dystrophy (OPMD) and myasthenia gravis are both rare conditions of different pathophysiological nature, so a fortuitous association is unlikely. However, antiacetylcholine receptor antibodies may be found in other genetic myopathies and this is probably not coincidental. Muscle fibre degeneration can induce innate immune responses that may break immune tolerance and allow the generation of autoantibodies to muscle proteins. We report a patient with atypical OPMD who also had acetylcholine receptor antibody-mediated myasthenia gravis. This report raises awareness of the diagnostic and treatment implications of the association of myasthenia gravis with genetic myopathies.

Congenital myasthenic syndrome in China: genetic and myopathological characterization

OBJECTIVE

We aimed to summarize the clinical, genetic, and myopathological features of a cohort of Chinese patients with congenital myasthenic syndrome, and follow up on therapeutic outcomes.

METHODS

The clinical spectrum, mutational frequency of genes, and pathological diagnostic clues of various subtypes of patients with congenital myasthenic syndrome were summarized. Therapeutic effects were followed up.

RESULTS

Thirty-five patients from 29 families were recruited. Ten genes were identified: GFPT1 (27.6%), AGRN (17.2%), CHRNE (17.2%), COLQ (13.8%), GMPPB (6.9%), CHAT, CHRNA1, DOK7, COG7, and SLC25A1 (3.4% each, respectively). Sole limb-girdle weakness was found in patients with AGRN (1/8) and GFPT1 (7/8) mutations, whereas distal weakness was all observed in patients with AGRN (6/8) mutations. Tubular aggregates were only found in patients with GFPT1 mutations (5/6). The patients with GMPPB mutations (2/2) had decreased alpha-dystroglycan. Acetylcholinesterase inhibitor therapy resulted in no response or worsened symptoms in patients with COLQ mutations, a diverse response in patients with AGRN mutations, and a good response in patients with other subtypes. Albuterol therapy was effective or harmless in most subtypes. Therapy effects became attenuated with long-term use in patients with COLQ or AGRN mutations.

INTERPRETATION

The genetic distribution of congenital myasthenic syndrome in China is distinct from that of other ethnic origins. The appearance of distal weakness, selective limb-girdle myasthenic syndrome, tubular aggregates, and decreased alpha-dystroglycan were indicative of the specific subtypes. Based on the follow-up findings, we suggest cautious evaluation of the long-term efficacy of therapeutic agents in congenital myasthenic syndrome.

Pharmacological Strategy for Congenital Myasthenic Syndrome with CHRNE Mutations: A Meta-Analysis of Case Reports

BACKGROUND

Congenital myasthenic syndromes (CMSs) are a heterogeneous group of neuromuscular disorders. Mutations of the nicotinic acetylcholine receptor epsilon subunit gene (CHRNE) are the most common causes of these disorders. CMSs are gaining increasing recognition by clinicians. However, pharmacological treatment of CMS with CHRNE mutations has only been discussed in a small number of case reports.

OBJECTIVE

This study aims to determine how to choose an appropriate pharmacological strategy for CMS with CHRNE mutations.

METHODS

A meta-analysis was performed. PubMed, MEDLINE, Web of Science, and Cochrane Library databases were searched for studies published in English prior to June 1, 2020. The extracted data included clinical information, gene mutations, pharmacological treatment, and treatment effects.

RESULTS

A total of 48 studies and 208 CMS patients with CHRNE mutations were included in our meta-analysis. Ten different pharmacological strategies were used in these patients. Our research found that β2-adrenergic receptor agonists had the best treatment effect for CMS patients with CHRNE mutations, especially in patients with primary AChR deficiency. In addition, our analysis found no evidence that age at disease onset influences the treatment results.

CONCLUSION

This meta-analysis provides evidence that (1) β2-adrenergic receptor agonist therapy could be the first choice of pharmacological strategy for treating CMS with CHRNE mutations; (2) a single-drug-regime, rather than a combination therapy, should be the first choice of treatment; and (3) it is never too late to initiate pharmacological treatment.

Congenital myasthenic syndrome with novel pathogenic variants in the COLQ gene associated with the presence of antibodies to acetylcholine receptors

Congenital myasthenic syndrome (CMS) is a heterogeneous group of inherited disorder which does not associate with anti-acetylcholine receptor (AChR) antibody. The presence of AChR autoantibody is pathogenic and highly sensitive and specific for autoimmune myasthenia gravis (MG). We describe 2 children from unrelated families who presented with hypotonia, ptosis and fatigability in early infancy with anti-AChR antibodies detected via ELISA on 2 separate occasions in the sera. Both were treated as refractory autoimmune MG due to poor clinical response to acetylcholinesterase inhibitor and immunotherapy. In view of the atypical clinical features, genetic studies of CMS were performed and both were confirmed to have novel pathogenic mutations in the COLQ gene. To the best of our knowledge, the presence of anti-AChR antibody in COLQ-related CMS has never been reported in the literature. The clinical presentation of early onset phenotype, and refractoriness to acetylcholinesterase inhibitor and immunotherapy should prompt CMS as a differential diagnosis.