242nd ENMC International Workshop: Diagnosis and management of juvenile myasthenia gravis Hoofddorp, the Netherlands, 1-3 March 2019

Treatment Patterns and Disease Burden of Juvenile Myasthenia Gravis in the United States: A Cohort Study Using Health Care Claims Databases

BACKGROUND AND OBJECTIVES

Juvenile myasthenia gravis (JMG) is a rare disorder defined as MG in patients younger than 18 years. Generalized JMG is more common in postpubertal than prepubertal patients. There are no formal international JMG treatment guidelines, and knowledge on treatment patterns and disease burden is limited. The aim of this study was to describe treatment patterns and health care resource utilization (HCRU) for patients with JMG and explore differences in disease presentation between prepubertal-onset (younger than 12 years) and postpubertal-onset (12-17 years) patients.

METHODS

Patients with JMG, newly diagnosed from 2008 to 2021, were identified from the US Merative MarketScan® Research Databases. Patients were followed from the first JMG claim (diagnosis/treatment with acetylcholinesterase inhibitors, immunoglobulin [Ig], or plasma exchange [PLEX]). The primary outcome was JMG-related treatment changes during follow-up, assessed descriptively. Rates of MG exacerbation, thymectomy, and acute intravenous immunoglobulin/PLEX treatment were assessed. HCRU was evaluated.

RESULTS

A total of 630 patients (64.1% female; mean [SD] age 9.07 [5.73] years; 57.6% prepubertal onset) were followed for a median (range) of 2.4 (0-13) years. Corticosteroids were started at a median (range) of 1.28 (0-37.02) and 3.19 (0-87.68) months from diagnosis for postpubertal-onset and prepubertal-onset patients, respectively. The rate of thymectomy was highest during treatment with maintenance Ig/PLEX (incidence rate [IR]; [95% CI] per 100 patient-years: 34.62 [14.41-83.17] for postpubertal-onset and 24.24 [9.10-64.60] for prepubertal-onset patients). MG exacerbations were most frequent during the first year of follow-up in both subgroups (34.1% and 30.3%). In postpubertal-onset patients, exacerbation was highest during treatment with maintenance Ig/PLEX and nonsteroid immunosuppressant therapy ([NSIST], mostly polytherapy) (IR [95% CI] 105.81 [68.99-162.29] and 91.22 [65.80-126.47]). For prepubertal-onset patients, exacerbation was most frequent during NSIST (polytherapy) and biologic treatment (IR [95% CI] 140.44 [115.45-170.85] and 142.95 [46.10-443.23]). JMG-related hospitalizations occurred in 36.0% and 30.0% of postpubertal-onset and prepubertal-onset patients, in the first year of follow-up.

DISCUSSION

Patients with JMG escalated rapidly through the treatment hierarchy. Postpubertal-onset patients escalated more quickly to later-line treatments than prepubertal-onset patients. However, some patients continued to experience high HCRU, highlighting the need for new JMG treatments to provide rapid disease control. A limitation is that treatment escalation reasons were not evaluated.

Epidemiology and 10-year clinical care of juvenile myasthenia gravis in England: a retrospective cohort study

Background

Published evidence is limited on the clinical burden of juvenile myasthenia gravis (JMG). We aimed to assess epidemiology and the clinical characteristics of JMG in England.

Methods

We performed a retrospective analysis of patients with newly diagnosed JMG identified in England via primary care and hospital data between 2010 and 2019.

Results

32 children (aged 2-17 years) with newly diagnosed JMG were included. Prevalence of JMG ranged from 2.2 (95% CI 1.5 to 3.1) in 2012 to 2.5 (95% CI 1.8 to 3.4) per 100 000 in 2018. The annual incidence ranged from 0.8 (95% CI 0.1 to 5.7) in 2015 to 3.8 (95% CI 1.6 to 9.0) per million per year in 2017. Incidence fluctuated in females from 1.6 (95% CI 0.2 to 11.3) in 2016 to 6 (95% CI 2.3 to 16.1) per million per year in 2018. Overall, 20 patients received first acetylcholinesterase inhibitors or corticosteroids with no prior therapy during the study period. During the follow-up period (median, 3.3 years), 17 patients (53.1%) with JMG experienced a hospitalisation. No deaths were observed.

Conclusions

This study confirms the rarity of JMG in England, with steady incidence and prevalence rates over a decade. Further research is required to assess unmet needs in JMG therapy and the importance of effective treatments for this condition.

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.

275th ENMC international workshop: Seronegative myasthenia gravis: An update paradigm for diagnosis and management, 9-11 February 2024, Hoofddorp, the Netherlands

The 275th ENMC workshop on the diagnosis and management of seronegative myasthenia gravis (SNMG) was held on February 9-11, 2024. The participants included experts in the field of adult and pediatric MG together with patient representatives. This workshop aimed to redefine SNMG in view of recent diagnostic and therapeutic updates and to identify patient unmet needs. The workshop has highlighted considerable challenges in the SNMG diagnostic work-up. To date, SNMG confirmation is often controversial, given the absence of specific diagnostic tests; no recommendations from international panels of experts are available in literature; myopathies, congenital myasthenic syndromes and functional disorders are the commonest misdiagnoses. Improving the disease diagnosis is crucial to avoid long delays in receiving appropriate treatment. To this purpose, a comprehensive diagnostic algorithm achieved consensus. Moreover, a remarkable variability in SNMG response to therapy and long-term prognosis has also been highlighted.

Comparison of juvenile and adult myasthenia gravis in a French cohort with focus on thymic histology

Myasthenia gravis (MG) is an autoimmune disease characterized by muscle fatigability due to acetylcholine receptor (AChR) autoantibodies. To better characterize juvenile MG (JMG), we analyzed 85 pre- and 132 post-pubescent JMG (with a cutoff age of 13) compared to 721 adult MG patients under 40 years old using a French database. Clinical data, anti-AChR antibody titers, thymectomy, and thymic histology were analyzed. The proportion of females was higher in each subgroup. No significant difference in the anti-AChR titers was observed. Interestingly, the proportion of AChR+ MG patients was notably lower among adult MG patients aged between 30 and 40 years, at 69.7%, compared to over 82.4% in the other subgroups. Thymic histological data were examined in patients who underwent thymectomy during the year of MG onset. Notably, in pre-JMG, the percentage of thymectomized patients was significantly lower (32.9% compared to more than 42.5% in other subgroups), and the delay to thymectomy was twice as long. We found a positive correlation between anti-AChR antibodies and germinal center grade across patient categories. Additionally, only females, particularly post-JMG patients, exhibited the highest rates of lymphofollicular hyperplasia (95% of cases) and germinal center grade. These findings reveal distinct patterns in JMG patients, particularly regarding thymic follicular hyperplasia, which appears to be exacerbated in females after puberty.

The Clinical Course and Treatment of a Case of Refractory Systemic Juvenile Myasthenia Gravis Successfully Treated with Thymectomy

Juvenile myasthenia gravis (JMG) exhibits a more favorable response to glucocorticoids and has a better prognosis than adult myasthenia gravis. However, no established treatment exists for refractory JMG. Although thymectomy has been performed in several patients with refractory systemic JMG, there are few detailed clinical descriptions of patients who underwent thymectomy. Here, we present the case of a 10-year-old boy with refractory systemic JMG who was successfully treated with thymectomy. The patient developed symptoms, including dysphagia, malaise, diurnal ptosis, and weakness in the trunk muscles, and he was diagnosed with generalized JMG. Despite undergoing various treatments, including steroids, tacrolimus, steroid pulse therapy, intravenous immunoglobulin, azathioprine (AZT), and rituximab, his symptoms did not improve. Therefore, he underwent a thoracoscopic thymectomy 24 months after disease onset. Thymectomy led to remission, as demonstrated by a significant reduction in the quantitative myasthenia gravis score and anti-acetylcholine receptor antibody levels, which persisted for 43 months after surgery. Our case demonstrates the effectiveness of thymectomy in systemic JMG patients with positive anti-acetylcholine receptor antibodies, despite therapeutic failure with AZT and rituximab, within 2 years of disease onset.

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.

Effects of Plasma Exchange Combined with Immunoglobulin Therapy on Consciousness, Immune Function, and Prognosis in Patients with Myasthenia Gravis Crisis: A Prospective Randomized Test

Background

Myasthenia gravis (MG) is an acquired autoimmune disease. The main clinical features of MG are skeletal muscle fatigue and pathological fatigue, which worsen at night or after fatigue, such as dyspnea, dysphagia, and systemic weakness. Plasma exchange (PE) is often used in patients with acute exacerbation of MG. Intravenous immunoglobulin (IVIG) is a collection of immunoglobulins from thousands of donors. IVIG can replace a variety of immunosuppressants or PE. However, the effect of PE or IVIG on patients' consciousness, immune function, and prognosis is not clear.

Objective

A prospective randomized test of the effects of PE combined with immunoglobulin on consciousness, immune function, and prognosis in patients with myasthenia gravis crisis (MGC).

Methods

Sixty patients with MGC treated from February 2019 to April 2021 were enrolled in our hospital. The cases who received PE were set as the PE group, and those who received PE combined with immunoglobulin were set as the PE+immunoglobulin group. The efficacy, clinical score, state of consciousness, immune function, acetylcholine receptor antibody (AChR-Ab), lymphocyte (LYM), albumin (ALB) levels, and the incidence of adverse reactions were compared.

Results

The improvement rate was 100.005% in the treatment group and 83.33% in the PE group. After treatment, the clinical score of the PE+immunoglobulin group was lower than that of the PE group, and the clinical relative score of the PE+immunoglobulin group was higher than that of the PE group (P < 0.05). The number of conscious people in the PE+immunoglobulin group was more than that in the PE group (P < 0.05). Immunoglobulin A, immunoglobulin M, immunoglobulin G, and immunoglobulin G in the PE+immunoglobulin group were higher than those in the PE group (P < 0.05). The levels of AChR-Ab and ALB in the PE+immunoglobulin group were higher than those in the PE group, while the level of LYM in the PE+immunoglobulin group was lower than that in the PE group. The incidence of skin system, gastrointestinal system, nervous system, and systemic damage in the PE+immunoglobulin group was lower than that in the PE group (P < 0.05).

Conclusion

The treatment of MGC with PE combined with immunoglobulin can not only effectively enhance the consciousness and immune function of patients but also effectively promote the prognosis, and the safety of treatment can be guaranteed.

Rituximab Therapy in the Treatment of Juvenile Myasthenia Gravis: The French Experience

OBJECTIVE

Corticosteroids are the first-line immunosuppressants in the management of juvenile myasthenia gravis despite their adverse effects. The place of new immunosuppressive therapies is not clearly defined by the last international consensus held in March 2019, due to the lack of clinical trials. The aim of this study is to describe the use of rituximab, its efficacy and safety in 8 main pediatric centers of the French neuromuscular reference network in order to propose a new place in the therapeutic strategy of juvenile myasthenia gravis.

METHOD

We conducted a retrospective multicenter study from January 1, 2009 to April 30, 2020, including a large cohort of children with myasthenia gravis in 8 main French pediatric reference centers of the Filnemus network. The type of myasthenia, the different lines of immunosuppressive treatment and the clinical course of the patients were collected. To evaluate the efficacy of rituximab, we studied the clinical course of patients on immunosuppressive therapy. Outcome was defined as the clinical and therapeutic status of patients at the last visit: stable without immunosuppressants, stable with immunosuppressants or unstable.

RESULTS

We included 74 patients: 18 children with ocular form and 56 children with generalized form. Of the 37 patients who required immunosuppressive therapy, 27 were treated with rituximab. Patients treated with rituximab had a better outcome than patients treated with conventional immunosuppressants (p = 0.006). The use of rituximab as a first-line immunosuppressant showed a better efficacy with a discontinuation of immunosuppressants in 75% of patients (vs. 25%, p=0.04) and resulted cortisone sparing (42% vs. 92%, p=0.03) compared with rituximab treatment as a second or third-line immunosuppression. Rituximab was well tolerated; no adverse effect was observed.

CONCLUSION

The use of rituximab has increased in France over the last 10 years as first line immunosuppressant. This study suggests a good tolerability and efficacy of rituximab in juvenile myasthenia gravis. Early use appears to improve outcomes and facilitate cortisone-sparing in antibody-positive generalized juvenile myasthenia.

CLASSIFICATION OF EVIDENCE

This study provides Class III evidence that for children with MG rituximab is effective and well tolerated.

The Epidemiology and Phenotypes of Ocular Manifestations in Childhood and Juvenile Myasthenia Gravis: A Review

Myasthenia gravis (MG) appears to have a similar incidence among adult populations worldwide. However, epidemiological and phenotypic differences have been noted among children and juveniles with MG. We reviewed the literature on childhood- and juvenile-onset MG among different populations, with the focus on ocular involvement, antibody profiles, the genetic susceptibility to juvenile MG phenotypes, the use of immune treatments, and the reported responses of extraocular muscles to therapies. Although epidemiological studies used different methodologies, reports from Asia, compared to Europe, showed more than two-fold higher proportions of prepubertal onset (before 12 years) vs. postpubertal-onset juveniles with MG. Compared to European children, ocular MG was 4-fold more frequent among Asian children, and 2–3-fold more frequent among children with African ancestry both in prepubertal and postpubertal ages at onset. These results suggest genetic influences. In Asia, HLA-B^*46 and DRB1^*09 appeared overrepresented in children with ocular MG. In Europe, children with MG had a significantly higher rate of transforming from ocular to generalized disease and with an overrepresentation of HLADRB1^*04. Although treatment regimens vary widely and the responses to immune therapies of the ocular muscles involved in MG were generally poorly described, there were indications that earlier use of steroid therapy may have better outcomes. Reports of treatment-resistant ophthalmoplegia may be more frequent in African and Asian juvenile MG cohorts compared to Europeans. Genetic and muscle gene expression studies point to dysregulated muscle atrophy signaling and mitochondrial metabolism pathways as pathogenetic mechanisms underpinning treatment-resistant ophthalmoplegia in susceptible individuals. In conclusion, phenotypic differences in juveniles with ocular manifestations of MG were evident in different populations suggesting pathogenetic influences. Treatment responses in MG-associated ocular disease should attract more careful descriptive reports. In MG, extraocular muscles may be vulnerable to critical periods of poor force generation and certain individuals may be particularly susceptible to developing treatment-resistant ophthalmoplegia. The development of prognostic biomarkers to identify these susceptible individuals is an unmet need.

Vaccination in pediatric acquired inflammatory immune-mediated neuromuscular disorders

AIM

To analyse literature data on vaccine related induction, worsening of the disease and disease reccurrences as well as vaccine safety and efficacy among pediatric patients with acquired inflammatory immune-mediated neuromuscular disorders (NMD).

METHODS

Medline, Pub Med and Scopus database search from 1975 to 2020 focused on pediatric age was conducted including peer reviews, meta analyses and epidemiological studies on vaccination and Guillain-Barré syndrome (GBS), Bell's palsy, optic neuritis (ON), myasthenia gravis (MG), chronic inflammatory demyelinating polyneuropathy (CIDP) and immune-mediated inflammatory myopathy (IM).

RESULTS AND CONCLUSION

s: There are no strong evidence supporting relationship between vaccination with different pediatric vaccines and development of first episodes or reccurrences of GBS, Bell's palsy, optic neuritis (ON), juvenile MG, CIDP, and IM. The vaccination and revaccination with inactivated vaccines is considered safe in children with medical history of GBS, Bell's palsy, ON, MG and IM. Caution when immunization against influenza, quadrivalent conjugated meningococcal vaccine (MCV4) and pneumococcal disease and avoiding tetanus toxoid immunization in CIDP patients is suggested. Patients with immune mediated acquired NMD should be vaccinated with live vaccines before the initiation of immunosupressive treatment. Immunosuppressed patients with low protective antibody titers should be considered for revaccination.

Management of Juvenile Myasthenia Gravis

Juvenile Myasthenia Gravis (JMG) is a rare disorder, defined as myasthenia gravis in children younger than 18 years of age. While clinical phenotypes are similar to adults, there are a number of caveats that influence management: broader differential diagnoses; higher rates of spontaneous remission; and the need to initiate appropriate treatment early, to avoid the long-term physical and psychosocial morbidity. Current practice is taken from treatment guidelines for adult MG or individual experience, with considerable variability seen across centers. We discuss our approach to treating JMG, in a large specialist JMG service, and review currently available evidence and highlight potential areas for future research. First-line treatment of generalized JMG is symptomatic management with pyridostigmine, but early use of immunosuppression, where good control is not achieved is important. Oral prednisolone is used as first-line immunosuppression with appropriate prevention and monitoring of side effects. Second-line therapies including azathioprine and mycophenolate may be considered where there is: no response to steroids, inability to wean to a reasonable minimum effective dose or if side-effects are intolerable. Management of ocular JMG is similar, but requires close involvement of ophthalmology in young children to prevent amblyopia. Muscle-specific tyrosine kinase (MuSK)-JMG show a poorer response to pyridostigmine and anecdotal evidence suggests that rituximab should be considered as second-line immunosuppression. Thymectomy is indicated in any patient with a thymoma, and consideration should be given in acetylcholine receptor (AChR) positive JMG allowing time for spontaneous remission. The benefit is less clear in ocular JMG and is not advised in MuSK-JMG. Children experiencing a myasthenic crisis require urgent hospital admission with access to the intensive care unit. PLEX is preferred over IVIG due to rapid onset of action, but this needs to be balanced with feasibility in very young children. Key questions remain in the management of JMG: when to initiate both first- and second-line treatments, choosing between steroid-sparing agents, and determining the optimal dose and treatment duration. We feel that given the rarity of this disease, the establishment of national registries and collaboration across groups will be needed to address these issues and facilitate future drug trials in JMG.