Update on juvenile myasthenia gravis

Targeted Treatments for Myasthenia Gravis in Children and Adolescents

Myasthenia gravis (MG) is an antibody-mediated disorder of the neuromuscular junction affecting children and adults. MG is a treatable condition with most patients requiring immunosuppression for disease control and/or remission. Juvenile myasthenia gravis (JMG) is rare in comparison with adult-onset MG but given the same underlying pathophysiology, treatment strategies are similar to those in adults. Until recently, there were only a few randomised controlled trials (RCTs) for MG treatments in adults and none in children, and management strategies were primarily based on expert consensus. In addition, treatment options for refractory MG cases have been severely limited, resulting in poor long-term quality of life in such patients due to the significant disease burden. Recently, there have been several RCTs focussing on novel therapeutic strategies with potentially promising outcomes, suggesting a change in MG management over the coming years and access to more effective and faster-acting drugs for MG patients. This paper will review current and new MG treatments including efgartigimod, eculizumab, rozanolixizumab, ravulizumab, and zilucoplan, with a focus on juvenile myasthenia gravis.

Juvenile ocular myasthenia gravis: a report of two cases

We report 2 cases of pediatric ocular myasthenia gravis. The first case was a 7-year-old girl who presented with bilateral ophthalmoplegia and ptosis that correlated with the onset of upper respiratory symptoms. Neuroimaging and acetylcholine receptor antibody testing were unremarkable. The ice pack test was positive. Symptoms greatly improved with pyridostigmine, with full resolution of ophthalmoplegia achieved by 8-month follow-up. The second case was a 4-year-old girl who presented emergently with ptosis and bilateral ophthalmoplegia. Acetylcholine receptor antibodies testing was positive. The patient was started on pyridostigmine and intravenous immunoglobulin and is scheduled to follow-up with pediatric ophthalmology in the outpatient setting.

Diagnostic dilemmas and challenges in the management of myasthenia in infants and toddlers: A case report

Myasthenia in the infancy and toddler age group is rare and often presents a challenge to treating pediatric neurologists. Our report addresses the challenges encountered when distinguishing myasthenia in infants and toddlers from similar illnesses, as well as the differentiation between congenital myasthenia, transient myasthenia, and autoimmune myasthenia. We present four cases of myasthenia between the ages of 10 and 30 months. The diagnosis and management of these cases were challenging due to the variability in clinical presentation. Four cases of myasthenia were diagnosed, with three having autoimmune myasthenia and one having congenital myasthenic syndrome. One patient initially tested negative for acetylcholine receptor antibodies, but later tested positive after 4 months and had a rare facial diplegia finding. The patient with congenital myasthenic syndrome had a novel genetic mutation, DPAGT1 homozygous variants, and also had false positive acetylcholine receptor antibodies. These cases highlight the importance of genetic testing for all infants and toddlers suspected of having myasthenia.

Anti-Inflammatory and Immunomodulatory Effect of High-Dose Immunoglobulins in Children: From Approved Indications to Off-Label Use

BACKGROUND

The large-scale utilization of immunoglobulins in patients with inborn errors of immunity (IEIs) since 1952 prompted the discovery of their key role at high doses as immunomodulatory and anti-inflammatory therapy, in the treatment of IEI-related immune dysregulation disorders, according to labelled and off-label indications. Recent years have been dominated by a progressive imbalance between the gradual but constant increase in the use of immunoglobulins and their availability, exacerbated by the SARS-CoV-2 pandemic.

OBJECTIVES

To provide pragmatic indications for a need-based application of high-dose immunoglobulins in the pediatric context.

SOURCES

A literature search was performed using PubMed, from inception until 1st August 2023, including the following keywords: anti-inflammatory; children; high dose gammaglobulin; high dose immunoglobulin; immune dysregulation; immunomodulation; immunomodulatory; inflammation; intravenous gammaglobulin; intravenous immunoglobulin; off-label; pediatric; subcutaneous gammaglobulin; subcutaneous immunoglobulin. All article types were considered.

IMPLICATIONS

In the light of the current imbalance between gammaglobulins' demand and availability, this review advocates the urgency of a more conscious utilization of this medical product, giving indications about benefits, risks, cost-effectiveness, and administration routes of high-dose immunoglobulins in children with hematologic, neurologic, and inflammatory immune dysregulation disorders, prompting further research towards a responsible employment of gammaglobulins and improving the therapeutical decisional process.

Outcome and clinical features in juvenile myasthenia gravis: A systematic review and meta-analysis

Background

Juvenile myasthenia gravis (JMG) is a rare autoimmune disease that has so far only been described in small cohort studies. We defined the clinical characteristics, management, and outcomes of JMG patients over the past 22 years.

Methods

A search of PubMed, EMBASE, and web of science (1/2000–2/2022) identified all English language and human studies of JMG. The population was patients diagnosed with JMG. Outcomes included the history of myasthenic crisis, autoimmune comorbidity, mortality, and treatment outcome. Data extraction was performed by independent reviewers. And we performed a pooled reanalysis of all published data in the included studies and compared with other studies of adult cohorts.

Results

We identified 11 articles describing 1,109 patients diagnosed between 2006 and 2021. JMG occurred in 60.4% of female patients. The mean age at presentation was 7.38 years old, and 60.6% of the patients had ocular symptoms as the first clinical manifestation. The most common initial presentation was ptosis, which occurred in 77.7% patients. AchR-Ab positive accounted for 78.7%. 641 patients received thymus examination, found to have thymic hyperplasia in 64.9% and thymoma in 2.2%. Autoimmune comorbidity was found in 13.6% and the most common one is thyroid disease (61.5%). First-line therapy, including pyridostigmine and steroids, was initiated in 97.8 and 68.6%, respectively. Six patients resolved spontaneously without treatment. Thymectomy was performed in 45.6%. 10.6% of patients had a history of myasthenic crisis. Completely stable remission was achieved in 23.7% and mortality was reported in 2 studies, which reported 8 deaths.

Conclusion

JMG is a rare disease with a relatively benign course, and differs from adult MG in some clinical features. The treatment regimen guideline for children is still not well-established. There is a need for prospective studies to properly evaluate treatment regimes.

Esophageal dysphagia in neuromuscular disorder patients with validity and reliability study of the brief esophageal dysphagia questionnaire

Esophageal dysphagia (ED) is often underestimated in neuromuscular disorders (NMD) and it is important to evaluate the esophageal phase of swallowing with an easy and rapid screening test. We aimed both to assess the prevalence of ED in NMD and to perform validity and reliability study of the brief easophageal dysphagia questionnaire (BEDQ) screening test in NMD patients. This prospective cross-sectional clinical study was performed on NMD patients. Demographic features and disease characteristics were recorded. Endoscopic evaluation for oropharyngeal dysphagia (OD) and high-resolution esophageal manometry for ED were performed. In addition, the BEDQ and the 10-item eating assessment tool (EAT-10) were used to all subjects. Cronbach's α and principle components factor analysis (PFCA) with varimax rotation were used for reliability. The Chicago Classification version 3 (CCv3) level (high-resolution esophageal manometry) and EAT-10 was used for validity. A total of 50 patients were included in the study. Thirty-four (68%) patients were diagnosed with myasthenia gravis and 16 (32%) patients were diagnosed with myopathy. Esophageal dysphagia according to the CCv3 was found in 33 (66%) of patients. While the Cronbach's α was excellent as 0.937 for test overall the T-BEDQ scale. The PCFA included all scale items and resulted in a single factor (eigenvalue = 5.72, 71.5%). The all BEDQ scores were demonstrated good correlation with EAT-10 score and very good correlation with CCv3 level. Evaluation of swallowing in patients with NMD should include not only the oropharyngeal phase of swallowing, but also esophageal phase. For this purpose, the BEDQ can be used as a rapid, valid, and reliable test for the evaluation of ED.

Childhood-Onset Myasthenia Gravis Patients Benefited from Thymectomy in a Long-Term Follow-up Observation

INTRODUCTION

 The effect of thymectomy on the treatment of childhood-onset myasthenia gravis (CMG) remains debatable. The objective of this study was to evaluate the clinical outcome and relevant prognostic factors of thymectomy for CMG patients.

MATERIALS AND METHODS

 A total of 32 CMG patients who underwent thymectomy before 18 years of age were included in this retrospective study. Clinical state following thymectomy was assessed by quantified myasthenia gravis (QMG) scores, myasthenia gravis-related activities of daily living (MG-ADL) scores, and Myasthenia Gravis Foundation of America postintervention status. Repeated-measures analysis of variance (ANOVA) examined the changes in postoperative scores during the 5-year follow-up. Univariate logistic regression was applied to identify factors associated with short-term (1-year postoperation) and long-term (5-year postoperation) clinical outcomes.

RESULTS

 Repeated-measures ANOVA showed that QMG scores (F = 6.737, p < 0.001) and MG-ADL scores (F = 7.923, p < 0.001) decreased gradually with time. Preoperative duration (odds ratio [OR] = 0.85, 95% confidence interval [CI]: 0.73-1.00, p = 0.043), gender (OR = 0.19, 95% CI: 0.04-0.94, p = 0.041), and MG subgroup (OR = 13.33, 95% CI: 1.43-123.99, p = 0.023) were predictors for 1-year postoperative prognosis. Shorter disease duration (OR = 0.82, 95% CI: 0.70-0.97, p = 0.018) and generalized CMG (OR = 6.11, 95% CI: 1.06-35.35, p = 0.043) were found to have more favorable long-term results.

CONCLUSION

 Our results suggest that thymectomy is effective in treating CMG. Thymectomy could be recommended for CMG patients, especially for patients in the early course of GMG.

Extended thymectomy via subxiphoid uniportal Video-Assisted Thoracoscopic Surgery: A case report

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Minimally invasive thymectomy is the primary surgical means for myasthenia gravis.

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Subxiphoid VATS method has the benefit of less blood loss and shorter hospital stay.

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Subxiphoid surgical port placement eliminates postoperative intercostal neuralgia.

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Subxiphoid uniportal thymectomy is safe and feasible for selected patients.

Introduction and importance

Myasthenia gravis (MG) is a well-known disease in adults, but the prevalence in children population is low. One treatment option is thymectomy. Transsternal procedure have been the primary approach, but recent trends lean toward minimally invasive technique with triportal and, recently, uniportal thoracoscopic method. This is related to the suggested less blood loss and hospital length of stay.

Case presentation

Hereby we report a case of a 4-year-old boy suffering from Juvenile Myasthenia Gravis (JMG) with thymic hyperplasia who underwent extended thymectomy via subxiphoid uniportal Video-Assisted Thoracoscopic Surgery (VATS) in our hospital. Pathology evaluation reported a case of thymic hyperplasia. The postoperative outcome was uneventful and satisfactory.

Clinical discussion

Subxiphoid uniportal approach for thymectomy is relatively new and has not been widely reported. It is important to highlight its advantages and disadvantages compared to other means for thymectomy.

Conclusion

Subxiphoid uniportal VATS is a safe and feasible approach for thymectomy.

Developing outcome measures of disease activity in pediatric myasthenia

INTRODUCTION

Pediatric myasthenia encompasses juvenile myasthenia gravis (JMG) and congenital myasthenic syndrome (CMS), which are chronic disorders with fluctuating symptoms amenable to medical therapy. Disease activity and treatment response may be difficult to assess, but, unlike adults, outcome measures have not been developed in children.

METHODS

The study was performed in children (0-18 years of age) at the neuromuscular center of a pediatric hospital over a 3-year period. Patients were recruited prospectively as part of their routine clinical care. Demographic data, diagnosis (JMG/CMS), and the following scales were recorded at each visit: Myasthenia Gravis Foundation of America (MGFA) class, Myasthenia Gravis Composite (MGC), and Pediatric Myasthenia-Quality of Life 15 (PM-QOL15).

RESULTS

Thirty-three patients (24 JMG, 9 CMS) were included in the study, 22 had two or more visits. We established known-groups validity of the MGC and PM-QOL15 scores as compared with the MGFA class. To establish concurrent validity, we constructed a receiver-operating characteristic curve and calculated threshold values of MGC and PM-QOL15 with optimal sensitivity and specificity for identifying a patient with more severe (MGFA III or higher) disease. Finally, we demonstrated the concordance between the MGC and PM-QOL15 by their statistically significant positive Pearson and Spearman correlations.

DISCUSSION

Our study suggests that MGC and PM-QOL15 are important disease outcome measures in pediatric myasthenia that are easy to administer and provide reliable assessment of disease activity in the clinic setting. Further studies are needed to validate their use for pediatric clinical research trials.

Outcomes of Juvenile Myasthenia Gravis: A Comparison of Robotic Thymectomy With Medication Treatment

BACKGROUND

The study aimed to compare the clinical outcomes of patients with juvenile myasthenia gravis (MG) who underwent robotic thymectomy with that of those who only received medication therapy.

METHODS

We retrospectively reviewed patients who visited our institution for the diagnosis or treatment of MG with an age at onset younger than 18 years. Patients who underwent thymectomy comprised the surgical group and those who received only medication therapy comprised the nonsurgical group. The clinical outcomes were assessed according to the Myasthenia Gravis Foundation of America Post-Intervention Status.

RESULTS

Forty-seven patients (35 female, 12 male) were included as the surgical group and 20 patients (15 female, 5 male) comprised the nonsurgical group. Significant differences were observed between the surgical and nonsurgical groups in antibody against acetylcholinesterase receptor (91.5% vs 65%; P = .012), disease duration (median 16 [interquartile range, 7-25] months vs 96 [interquartile range, 42-480] months; P < .001), and corticosteroids requirement (53.2% vs 15%; P = .004) at baseline. Kaplan-Meier analysis showed a higher cumulative probability of complete stable remission in the surgical group (P = .002) compared with the nonsurgical group. Moreover, thymectomy (hazard ratio, 3.842; 95% confidence interval, 1.116-13.230; P = .033) and age at onset (hazard ratio, 0.89; 95% confidence interval, 0.80-0.99; P = .037) were still associated with the achievement of complete stable remission in the multivariable analysis. Furthermore, a significant steroid-sparing effect was observed in the surgical group but not in the nonsurgical group.

CONCLUSIONS

Robotic thymectomy seems to be more effective than medication therapy on juvenile MG in terms of inducing remission and reducing the use of corticosteroids.

[Clinical effect of tacrolimus in the treatment of myasthenia gravis in children]

OBJECTIVE

To evaluate the efficacy and safety of tacrolimus in the treatment of children with myasthenia gravis (MG).

METHODS

A total of 28 children with MG were treated with tacrolimus. MG-Activities of Daily Living (MG-ADL) scale was used to assess clinical outcome and safety after 1, 3, 6, 9, and 12 months of treatment.

RESULTS

After tacrolimus treatment, the MG-ADL score at 1, 3, 6, 9 and 12 months was lower than that at baseline (P<0.05), and the MG-ADL score showed a gradually decreasing trend. The response rates to tacrolimus treatment at 1, 3, 6, 9, and 12 months were 59%, 81%, 84%, 88%, and 88% respectively. At 6, 9, 12, and 18 months of treatment, 4, 13, 14, and 15 children respectively were withdrawn from prednisone. No recurrence was observed during treatment. Major adverse reactions/events were asymptomatic reduction in blood magnesium in 5 children and positive urine occult blood in 1 child, which turned negative without special treatment, and tacrolimus was not stopped due to such adverse reactions/events. One child was withdrawn from tacrolimus due to recurrent vomiting. According to CYP3A5 genotypes, all of the patients were divided into two groups: slow metabolic type (n=19) and non-slow metabolic type (fast metabolic type + intermediate type; n=9). The non-slow metabolism group received a higher dose of tacrolimus, but had a lower trough concentration of tacrolimus than the slow metabolism group (P<0.05). The slow metabolism group had a higher response rates to tacrolimus treatment than the non-slow metabolism group (P<0.05).

CONCLUSIONS

Tacrolimus appears to be effective and safe in the treatment of children with MG and is thus an option for immunosuppressive therapy. CYP3A5 genotyping has a certain guiding significance for determining the dosage of tacrolimus.

Autoimmune Channelopathies at Neuromuscular Junction

The neuromuscular junction, also called myoneural junction, is a site of chemical communication between a nerve fiber and a muscle cell. There are many types of channels at neuromuscular junction that play indispensable roles in neuromuscular signal transmission, such as voltage-gated calcium channels and voltage-gated potassium channels on presynaptic membrane, and acetylcholine receptors on post-synaptic membrane. Over the last two decades, our understanding of the role that autoantibodies play in neuromuscular junction disorders has been greatly improved. Antibodies against these channels cause a heterogeneous group of diseases, such as Lambert-Eaton syndrome, Isaacs' syndrome and myasthenia gravis. Lambert-Eaton syndrome is characterized by late onset of fatigue, skeletal muscle weakness, and autonomic symptoms. Patients with Isaacs' syndrome demonstrate muscle cramps and fasciculation. Myasthenia gravis is the most common autoimmune neuromuscular junction channelopathy characterized by fluctuation of muscle weakness. All these disorders have a high risk of tumor. Although these channelopathies share some common features, they differ for clinical features, antibodies profile, neurophysiological features, and treatments. The purpose of this review is to give a comprehensive insight on recent advances in autoimmune channelopathies at the neuromuscular junction.

Assessment of acute motor deficit in the pediatric emergency room

OBJECTIVES

This review article aimed to present a clinical approach, emphasizing the diagnostic investigation, to children and adolescents who present in the emergency room with acute-onset muscle weakness.

SOURCES

A systematic search was performed in PubMed database during April and May 2017, using the following search terms in various combinations: "acute," "weakness," "motor deficit," "flaccid paralysis," "child," "pediatric," and "emergency". The articles chosen for this review were published over the past ten years, from 1997 through 2017. This study assessed the pediatric age range, from 0 to 18 years.

SUMMARY OF THE DATA

Acute motor deficit is a fairly common presentation in the pediatric emergency room. Patients may be categorized as having localized or diffuse motor impairment, and a precise description of clinical features is essential in order to allow a complete differential diagnosis. The two most common causes of acute flaccid paralysis in the pediatric emergency room are Guillain-Barré syndrome and transverse myelitis; notwithstanding, other etiologies should be considered, such as acute disseminated encephalomyelitis, infectious myelitis, myasthenia gravis, stroke, alternating hemiplegia of childhood, periodic paralyses, brainstem encephalitis, and functional muscle weakness. Algorithms for acute localized or diffuse weakness investigation in the emergency setting are also presented.

CONCLUSIONS

The clinical skills to obtain a complete history and to perform a detailed physical examination are emphasized. An organized, logical, and stepwise diagnostic and therapeutic management is essential to eventually restore patient's well-being and full health.

Clinical features and evolution of juvenile myasthenia gravis in a French cohort

INTRODUCTION

In this study we determined the clinical, paraclinical, and treatment-related features of juvenile myasthenia gravis (JMG) as well as the clinical course in a cohort of French children.

METHODS

We conducted a retrospective study of 40 patients with JMG at 2 French pediatric neurology departments from April 2004 to April 2014.

RESULTS

Among the patients, 70% had generalized JMG, 52% had positive acetylcholine receptor antibodies, 8% had muscle-specific kinase antibodies, and 40% were seronegative. Treatment with acetylcholinesterase inhibitors was effective and sufficient in 47% of patients. The 6 patients with generalized JMG treated with rituximab and/or immunoadsorption showed improvement. Thirty percent of the patients required hospitalization in an intensive care unit during follow-up (mean 4.7 years). Remission without treatment occurred in 18% of patients.

DISCUSSION

As with adults, JMG has high morbidity, particularly among children with generalized symptoms, and rituximab should be considered early in the course of the disease as a second-line treatment. Muscle Nerve 57: 603-609, 2018.

The role of thymectomy in the treatment of juvenile myasthenia gravis: a systematic review

BACKGROUND

The role of thymectomy in the treatment of juvenile myasthenia gravis (JMG) is poorly defined. The objective of this systematic review was to evaluate the effect of thymectomy on survival, disease severity, and peri-operative complications for patients with JMG.

METHODS

A search of MEDLINE, EMBASE, and the Cochrane Library (1/1/2000-3/1/2016) identified all English language, human studies of thymectomy for JMG. The population was patients with JMG age ≤18 years who underwent thymectomy (comparator group was unexposed to thymectomy). Outcomes included survival, disease severity, and post-operative complications. Data extraction was performed by independent reviewers.

RESULTS

Sixteen retrospective studies included 1131 participants with JMG and 488 (43%) underwent thymectomy. Post-operative improvement in JMG severity occurred for 77% (n = 376/488). Comparisons of thymectomy to non-operative management were mixed. Post-operative complications were poorly recorded. Power to compare surgical approaches was limited. Outcomes specific to antibodies, surgical pathology findings, severity of JMG, and timing of thymectomy were sparse.

CONCLUSIONS

Existing data regarding thymectomy for JMG are limited and entirely retrospective. The majority of patients who underwent thymectomy had improvement in disease severity and post-operative complications were rare. Prospective, multicenter study of thymectomy for JMG is warranted.

Pediatric Myasthenia Gravis

Myasthenia gravis is a disorder of neuromuscular transmission that leads to fatigue of skeletal muscles and fluctuating weakness. Myasthenia that affects children can be classified into the following 3 forms: transient neonatal myasthenia, congenital myasthenic syndromes, and juvenile myasthenia gravis (JMG). JMG is an autoimmune disorder that has a tendency to affect the extraocular muscles, but can also affect all skeletal muscles leading to generalized weakness and fatigability. Respiratory muscles may be involved leading to respiratory failure requiring ventilator support. Diagnosis should be suspected clinically, and confirmatory diagnostic testing be performed, including serum acetylcholine receptor antibodies, repetitive nerve stimulation, and electromyography. Treatment for JMG includes acetylcholinesterase inhibitors, immunosuppressive medications, plasma exchange, intravenous immunoglobulins, and thymectomy. Children with myasthenia gravis require monitoring by a pediatric ophthalmologist for the development of amblyopia from ptosis or strabismus.

Juvenile Myasthenia Gravis in Korea: Subgroup Analysis According to Sex and Onset Age

Juvenile myasthenia gravis presents before 18 years of age with different characteristics according to racial background and pubertal development. The authors aimed to determine the clinical characteristics of children and adolescents of Korean ethnicity with myasthenia gravis, and evaluate the presentation and clinical outcomes according to the sex and onset age of the patients. The authors recruited 88 Korean juvenile myasthenia gravis patients between September 2005 and August 2015. Worse clinical severity from presentation, more aggressive treatment strategies, and worse final treatment outcomes were noted in girls with postpubertal onset than in the other patients. The symptoms were milder (pure ocular presentation in 96.6% [85/88]) and the disease course was more benign (94.3% [83/88]) in this study than in the literature. The homogenous racial background might have contributed to these results. These findings highlight the influence of pubertal development and the need for timely and appropriate active treatment, including thymectomy, to improve prognosis.

Feeding and Swallowing Disorders in Pediatric Neuromuscular Diseases: An Overview

Feeding and swallowing problems in infants and children have a great impact on health and wellbeing. The aim of this study was to provide an overview of recognized feeding and swallowing problems in different groups of children with neuromuscular diseases, based on relevant literature and expert opinion, and to propose recommendations for the assessment and treatment of these problems. Almost all pediatric neuromuscular diseases are accompanied by feeding and swallowing problems during the different phases of deglutition, problems that give rise to a wide variety of signs and symptoms, which emphasizes the importance of a comprehensive feeding and swallowing assessment by a speech and language therapist.

Neuromuscular disorders: from diagnosis to translational research, drug development and clinical trials

Pediatric neuromuscular disorders are a heterogeneous group of conditions that form four distinct groupings: (1) motor neuron diseases, (2) neuropathies, (3) disorders of the neuromuscular junction, and (4) myopathies.