The autoimmune spectrum of myasthenia gravis: a Swedish population-based study

Discovery of new myositis genetic associations through leveraging other immune-mediated diseases

Genome-wide association studies (GWASs) have been successful at finding associations between genetic variants and human traits, including the immune-mediated diseases (IMDs). However, the requirement of large sample sizes for discovery poses a challenge for learning about less common diseases, where increasing volunteer numbers might not be feasible. An example of this is myositis (or idiopathic inflammatory myopathies [IIM]s), a group of rare, heterogeneous autoimmune diseases affecting skeletal muscle and other organs, severely impairing life quality. Here, we applied a feature engineering method to borrow information from larger IMD GWASs to find new genetic associations with IIM and its subgroups. Combining this approach with two clustering methods, we found 17 IMDs genetically close to IIM, including some common comorbid conditions, such as systemic sclerosis and Sjögren's syndrome, as well as hypo- and hyperthyroidism. All IIM subtypes were genetically similar within this framework. Next, we colocalized IIM signals that overlapped IMD signals, and found seven potentially novel myositis associations mapped to immune-related genes, including BLK, IRF5/TNPO3, and ITK/HAVCR2, implicating a role for both B and T cells in IIM. This work proposes a new paradigm of genetic discovery in rarer diseases by leveraging information from more common IMD, and can be expanded to other conditions and traits beyond IMD.

Comorbidity in myasthenia gravis: multicentric, hospital-based, and controlled study of 178 Italian patients

BACKGROUND

Myasthenia gravis (MG) is an autoimmune disorder with fluctuating weakness that causes significant disability and morbidity. Comorbidities may influence the course of MG, particularly in specific subgroups. The aim of this study is to investigate the frequency of comorbidities in MG patients compared to healthy controls (HC) and to evaluate their distribution according to age at disease onset, sex, and disease severity.

METHODS

MG patients attending the University Hospital "Paolo Giaccone" in Palermo and "SS Annunziata" Hospital in Chieti were enrolled; HC were enrolled from the general population. Non-parametric statistics and logistic regression were used to assess the association of specific comorbidities according to age at disease onset, sex, disease subtypes, and severity of the disease.

RESULTS

A total of 356 subjects were included in the study: 178 MG patients (46% F; median age 60 years [51-71]) and 178 sex- and age-matched HC (46% F, median age 59 years [50-66]). Overall, 86% of MG patients and 76% of HC suffered from comorbidities, and MG patients had a higher number of comorbidities compared to HC. Patients with late-onset suffered from more comorbidities than those with early-onset MG. Hypertension was more common in male patients with MG, while thymic hyperplasia, osteoporosis, and autoimmune diseases were more common in females. Respiratory disorders and thymoma were more common in patients with more severe disease (p < 0.05 for all comparisons).

CONCLUSION

MG patients, particularly those with late onset, showed a higher prevalence of comorbidities than HC. Assessment of comorbidities in MG is an essential issue to identify the appropriate treatment and achieve the best management.

Genetic predisposition to autoimmune encephalitis and paraneoplastic neurological syndromes

PURPOSE OF REVIEW

We summarize the recent discoveries on genetic predisposition to autoimmune encephalitis and paraneoplastic neurological syndromes (PNS), emphasizing clinical and pathophysiological implications.

RECENT FINDINGS

The human leukocyte antigen (HLA) is the most studied genetic factor in autoimmune encephalitis and PNS. The HLA haplotype 8.1, which is widely known to be related to systemic autoimmunity, has been only weakly associated with a few types of autoimmune encephalitis and PNS. However, the strongest and most specific associations have been reported in a subgroup of autoimmune encephalitis that comprises antileucine-rich glioma-inactivated 1 (LGI1) limbic encephalitis, associated with DRB1∗07 : 01 , anticontactin-associated protein-like 2 (CASPR2) limbic encephalitis, associated with DRB1∗11 : 01 , and anti-IgLON5 disease, associated with DRB1∗10 : 01∼DQA1∗01∼DQB1∗05 . Non-HLA genes have been poorly investigated so far in autoimmune encephalitis, mainly in those lacking HLA associations such as anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis, with only a few genome-wide association studies (GWAS) reporting equivocal results principally limited by small sample size.

SUMMARY

Genetic predisposition seems to be driven mostly by HLA in a group of autoimmune encephalitis characterized by being nonparaneoplastic and having predominantly IgG4 autoantibodies. The contribution of non-HLA genes, especially in those diseases lacking known or strong HLA associations, will require large cohorts enabling GWAS to be powerful enough to render meaningful results.

Long-Term Healthcare Resource Utilization and Costs among Patients with Myasthenia Gravis: A Swedish Nationwide Population-Based Study

INTRODUCTION

Healthcare costs and societal impact of myasthenia gravis (MG), a potentially life-threatening rare, chronic neuromuscular disease, are sparsely studied. We assessed healthcare resource utilization (HCRU) and associated costs among patients with newly diagnosed (ND) and preexisting (PE) MG in Sweden.

METHODS

This observational, retrospective cohort study used data from four linkable Swedish nationwide population-based registries. Adult MG patients receiving pharmacological treatment for MG and having ≥24-month follow-up during the period January 1, 2010, to December 31, 2017, were included.

RESULTS

A total of 1,275 patients were included in the analysis, of which 554 patients were categorized into the ND MG group and 721 into the PE MG group. Mean (±SD) age was 61.3 (±17.4) years, and 52.3% were female. In the first year post-diagnosis, ND patients had significantly higher utilization of acetylcholinesterase inhibitors (96.0% vs. 83.9%), corticosteroids (59.6% vs. 45.8%), thymectomy (12.1% vs. 0.7%), and plasma exchange (3.8% vs. 0.6%); had higher all-cause (70.9% vs. 35.8%) and MG-related (62.5% vs. 18.4%) hospitalization rates with 11 more hospitalization days (all p < 0.01) and an increased risk of hospitalization (odds ratio [95% CI] = 4.4 [3.43, 5.64]) than PE MG. In year 1 post-diagnosis, ND MG patients incurred EUR 7,302 (p < 0.01) higher total all-cause costs than PE MG, of which 84% were estimated to be MG-related and the majority (86%) were related to inpatient care. These results remained significant also after controlling for baseline demographics and comorbidities (p < 0.01). In year 2 post-diagnosis, the all-cause medical costs decreased by ∼55% for ND MG from year 1 and were comparable with PE MG.

CONCLUSION

In this population-based study, MG patients required significantly more healthcare resources in year 1 post-diagnosis than PE MG primarily due to more pharmacological treatments, thymectomies, and associated hospitalizations. These findings highlight the need to better understand potential factors including disease characteristics associated with increased health resource use and costs and need for more efficacious treatments early in the disease course.

Myasthenia gravis and five autoimmune diseases: a bidirectional Mendelian randomization study

BACKGROUND

The association between myasthenia gravis (MG) and other autoimmune diseases is well established. In this study, we aimed to investigate the causal effects between MG and five other autoimmune diseases, including autoimmune thyroid disease (AITD), multiple sclerosis (MS), rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), and type 1 diabetes (T1DM).

METHODS

We conducted a bidirectional Mendelian randomization (MR) study by using seven published genome-wide association studies (GWAS), including MG (1873 patients versus 36,370 controls), AITD (autoimmune hypothyroidism) (22,997 patients versus 175,475 controls), AITD (autoimmune hyperthyroidism) (962 patients versus 172,976 controls), MS (47,429 patients versus 68,374 controls), RA (14,361 patients versus 43,923 controls), SLE (4222 patients versus 8431 controls), and T1DM (9266 patients versus 15,574 controls). We used the inverse-variance-weighted (IVW) method, weighted-median (WM) estimator, MR-Egger regression, and MR PRESSO in our analyses. We also carried out detailed sensitivity analyses for each direction using the aforementioned methods.

RESULTS

When MG was treated as the exposure, MR evidence suggested a causal relationship between MG and T1DM, SLE, AITD (both hypothyroidism and hyperthyroidism), and MS (excluding RA). Using the IVW method, we found that MG was associated with increased risk of T1DM (OR = 1.94; 95% CI, 1.16-3.26; p = 0.012), SLE (OR = 1.47; 95% CI, 1.02-2.13; p = 0.04), AITD (hypothyroidism) (OR = 1.31; 95% CI, 1.02-1.68; p = 0.039), AITD (hyperthyroidism) (OR = 1.55; 95% CI, 1.15-2.09; p = 0.004), and MS (OR = 1.46; 95% CI, 1.01-2.09; p = 0.041). When MG was treated as the outcome, MR evidence suggested that RA, T1DM, and SLE were causal factors in MG. Using the IVW method, we found that the risk of MG increased with exposure to RA (OR = 1.21; 95% CI, 1.08-1.37; p = 0.002), T1DM (OR = 1.09; 95% CI, 1.02-1.16; p = 0.006), and SLE (OR = 1.12; 95% CI, 1.02-1.23; p = 0.018).

CONCLUSIONS

This study demonstrated a causal relationship between MG and several other autoimmune diseases. Our results supported a bidirectional causal association between MG and SLE/T1DM. Our findings also provided reliable evidence that MG is associated with increased risk of AITD. Meanwhile, we also showed that RA is a possible causal driver of MG risk.

Bidirectional association between autoimmune disease and perinatal depression: a nationwide study with sibling comparison

Although major depression, characterized by a pro-inflammatory profile, genetically overlap with autoimmune disease (AD) and the perinatal period involve immune system adaptations and AD symptom alterations, the bidirectional link between perinatal depression (PND) and AD is largely unexplored. Hence, the objective of this study was to investigate the bidirectional association between PND and AD. Using nationwide Swedish population and health registers, we conducted a nested case-control study and a matched cohort study. From 1,347,901 pregnancies during 2001-2013, we included 55,299 incident PND, their unaffected full sisters, and 10 unaffected matched women per PND case. We identified 41 subtypes of AD diagnoses recorded in the registers and compared PND with unaffected population-matched women and full sisters, using multivariable regressions. Women with an AD had a 30% higher risk of subsequent PND (95% CI 1.2-1.5) and women exposed to PND had a 30% higher risk of a subsequent AD (95% CI 1.3-1.4). Comparable associations were found when comparing exposed women with their unaffected sisters (nested case-control OR: 1.3, 95% CI 1.2-1.5, matched cohort HR: 1.3, 95% CI 1.1-1.6), and when studying antepartum and postpartum depression. The bidirectional association was more pronounced among women without psychiatric comorbidities (nested case-control OR: 1.5, 95% CI 1.4-1.6, matched cohort HR: 1.4, 95% CI 1.4-1.5) and strongest for multiple sclerosis (nested case-control OR: 2.0, 95% CI 1.6-2.3, matched cohort HR: 1.8, 95% CI 1.0-3.1). These findings demonstrate a bidirectional association between AD and PND independent of psychiatric comorbidities, suggesting possibly shared biological mechanisms. If future translational science confirms the underlying mechanisms, healthcare providers need to be aware of the increased risk of PND among women with ADs and vice versa.

Epidemiology of myasthenia gravis in France: A retrospective claims database study (STAMINA)

BACKGROUND

The objectives of this observational study were to report the incidence and prevalence of myasthenia gravis (MG) in France, describe patients' characteristics and treatment patterns, and estimate mortality.

METHODS

A historical cohort analysis was performed using the French National Health Data System (SNDS) database between 2008 and 2020. Patients with MG were identified based on ICD-10 codes during hospitalization and/or long-term disease (ALD) status, which leads to a 100% reimbursement for healthcare expenses related to MG. The study population was matched to a control group based on age, sex and region of residence.

RESULTS

The overall incidence of MG was estimated at 2.5/100,000 in 2019 and the overall prevalence at 34.2/100,000. The mean age was 58.3 years for incident patients and 58.6 for prevalent patients. Among patients with MG, 57.1% were women. In the first year after identification of MG, acetylcholinesterase inhibitors were the most commonly used treatments (87.0%). Corticosteroids were delivered to 58.3% of patients, intravenous immunoglobulin to 34.4%, and azathioprine to 29.9%. Additionally, 8% of patients underwent thymectomy. The proportions of patients with exacerbations and crises were 59.7% and 13.5% respectively in the first year after MG identification. All-cause mortality was significantly higher in patients with MG compared to matched controls (HR=1.82 (95% CI [1.74;1.90], P<0.0001)).

CONCLUSION

In this study, the incidence and prevalence of MG estimated in France were found to be higher than previously reported. Most exacerbations and crises occurred within the first year after MG identification. MG was associated with increased mortality compared to a control population matched on age, gender, and geographical region.

Pregnancy outcomes for women with myasthenia gravis and their newborns: A nationwide register-based cohort study

BACKGROUND AND PURPOSE

Few large-scale studies examine whether maternal myasthenia gravis (MG) is a risk factor for complications during pregnancy and childbirth. This study evaluated whether maternal MG is associated with an increased risk of adverse pregnancy, delivery, and neonatal outcomes.

METHODS

We conducted a nationwide Swedish register-based cohort study of women who gave birth to singleton infants (≥22 gestational weeks) during 1987-2019. Exposed women were diagnosed with MG before or during the index pregnancy (N = 443). Unexposed women comprised 4249 women without a diagnosis of MG, matched for age, parity, hospital, and year of childbirth. The risks of adverse pregnancy, delivery, and neonatal outcomes for women with MG were estimated using regression modeling and presented as adjusted odds ratios (aOR).

RESULTS

There was no increased risk of pregnancy complications in women with MG. Women with MG had a spontaneous onset of labor less often than women without MG (69.8% vs. 79.5%; aOR 0.59; p < 0.001) as well as higher labor induction rates and elective cesarean section deliveries (16.0% vs. 12.3%, aOR 1.42; p = 0.02 and 12.0% vs. 8.1%, aOR 1.59; p = 0.009). Infants of women with MG were born on average 2 days earlier (p = 0.002); however, these infants did not have a higher risk of having low APGAR, being small for gestational age, or having a congenital malformation.

CONCLUSION

This first nationwide study of pregnancy in women with MG in Sweden demonstrates reassuring results overall, suggesting generally safe pregnancy outcomes for women with MG and their infants.

Pathophysiology of Childhood-Onset Myasthenia: Abnormalities of Neuromuscular Junction and Autoimmunity and Its Background

The pathophysiology of myasthenia gravis (MG) has been largely elucidated over the past half century, and treatment methods have advanced. However, the number of cases of childhood-onset MG is smaller than that of adult MG, and the treatment of childhood-onset MG has continued to be based on research in the adult field. Research on pathophysiology and treatment methods that account for the unique growth and development of children is now desired. According to an epidemiological survey conducted by the Ministry of Health, Labour and Welfare of Japan, the number of patients with MG by age of onset in Japan is high in early childhood. In recent years, MG has been reported from many countries around the world, but the pattern of the number of patients by age of onset differs between East Asia and Western Europe, confirming that the Japanese pattern is common in East Asia. Furthermore, there are racial differences in autoimmune MG and congenital myasthenic syndromes according to immunogenetic background, and their pathophysiology and relationships are gradually becoming clear. In addition, treatment options are also recognized in different regions of the world. In this review article, I will present recent findings focusing on the differences in pathophysiology.

Residual serum fibrinogen as a universal biomarker for all serotypes of Myasthenia gravis

Myasthenia Gravis (MG) is an autoimmune disease associated with severe neuromuscular weakness. Diagnostic confirmation of MG is typically delayed and secured in about 85% and 50% of patients with generalized and ocular MG, respectively with serum antibodies. We have identified a sensitive and specific diagnostic biomarker for various MG serotypes with quantitative proteomics. Serum proteomes of 18 individuals (MG patients, healthy controls (HC), Rheumatoid Arthritis (RA) were quantified in a pilot study and occurrence of high residual fibrinogen was validated by immunoblotting and further investigated by targeted mass spectrometry on the sera of 79 individuals (31 MG of various serotypes, 30 HC, 18 RA). Initial proteomic analysis identified high residual fibrinogen in MG patient sera which was then validated by antibody-based testing. Subsequently, a blinded study of independent samples showed 100% differentiation of MG patients from controls. A final serological quantification of 14 surrogate peptides derived from α-, β-, and γ-subunits of fibrinogen in 79 individuals revealed fibrinogen to be highly specific and 100% sensitive for MG (p < 0.00001), with a remarkable average higher abundance of > 1000-fold over control groups. Our unanticipated discovery of high levels of residual serum fibrinogen in all MG patients can secure rapid bedside diagnosis of MG.

Combined effect of thymectomy on myasthenia gravis in patients with concomitant auto-immune diseases: a 22-year single-center experience

Myasthenia gravis (MG) is an autoimmune disease (AD), and patients with MG often have other types of ADs. We analyzed the prognosis of patients with MG complicated by AD after thymectomy. A retrospective analysis was performed for patients with MG complicated by ADs treated surgically in our center over the past 22 years, and their general condition and follow-up data were collected and analyzed. 33 patients were included totally. 28 patients displayed improvement or even complete recovery of MG, and 23 of 36 ADs revealed improvement or even complete recovery. The prognosis of MG is significantly correlated with the duration of postoperative follow-up time (p = 0.028), and in patients with thymoma, the larger the tumor diameter, the better the prognosis of MG (p = 0.026). Thymic hyperplasia patients were predominantly female (p = 0.049) and young (p < 0.001). The most common concomitant AD in this study was a thyroid-associated AD, which was associated with thymic hyperplasia (p < 0.001), Osserman type I MG (p < 0.001), and young age (p < 0.001). Thymectomy had a good therapeutic effect on MG complicated by AD, and there was a close correlation between surgery, thymus, MG, and ADs.

Disease-Based Prognostication: Myasthenia Gravis

Myasthenia gravis (MG) is an acquired autoimmune neuromuscular junction transmission disorder that clinically presents as fluctuating or persistent weakness in various skeletal muscle groups. Neuroprognostication in MG begins with some basic observations on the natural history of the disease and known treatment outcomes. Our objective is to provide a framework that can assist a clinician who encounters the MG patient for the first time and attempts to prognosticate probable outcomes in individual patients. In this review article, we explore clinical type, age of onset, antibody status, severity of disease, thymus pathology, autoimmune, and other comorbidities as prognostic factors in MG.

Clinical features of myasthenia gravis with neurological and systemic autoimmune diseases

Multiple reports on the co-existence of autoimmune diseases and myasthenia gravis (MG) have raised considerable concern. Therefore, we reviewed autoimmune diseases in MG to explore their clinical presentations and determine whether the presence of autoimmune diseases affects the disease severity and treatment strategies for MG. We reviewed all the major immune-mediated coexisting autoimmune conditions associated with MG. PubMed, Embase and Web of Science were searched for relevant studies from their inception to January 2023. There is a higher frequency of concomitant autoimmune diseases in patients with MG than in the general population with a marked risk in women. Most autoimmune comorbidities are linked to AChR-MG; however, there are few reports of MuSK-MG. Thyroid disorders, systemic lupus erythematosus, and vitiligo are the most common system autoimmune diseases associated with MG. In addition, MG can coexist with neurological autoimmune diseases, such as neuromyelitis optica (NMO), inflammatory myopathy (IM), multiple sclerosis (MS), and autoimmune encephalitis (AE), with NMO being the most common. Autoimmune diseases appear to develop more often in early-onset MG (EOMG). MS coexists more commonly with EOMG, while IM coexists with LOMG. In addition, MG complicated by autoimmune diseases tends to have mild clinical manifestations, and the coexistence of autoimmune diseases does not influence the clinical course of MG. The clinical course of neurological autoimmune diseases is typically severe. Autoimmune diseases occur most often after MG or as a combined abnormality; therefore, timely thymectomy followed by immunotherapy could be effective. In addition, thymoma-associated AChR MG is associated with an increased risk of AE and IM, whereas NMO and MS are associated with thymic hyperplasia. The co-occurrence of MG and autoimmune diseases could be attributed to similar immunological mechanisms with different targets and common genetic factor predisposition. This review provides evidence of the association between MG and several comorbid autoimmune diseases.

Genetic Associations Between Stress-Related Disorders and Autoimmune Disease

Objective: Emerging evidence supports a bidirectional phenotypic association between stress-related disorders and autoimmune disease. However, the biological underpinnings remain unclear. Here, the authors examined whether and how shared genetics contribute to the observed phenotypic associations. Methods: Based on data from 4,123,631 individuals identified from Swedish nationwide registers, familial coaggregation of stress-related disorders (any disorder or posttraumatic stress disorder [PTSD]) and autoimmune disease were initially estimated in seven cohorts with different degrees of kinship. Polygenic risk score (PRS) analyses were then performed with individual-level genotyping data from 376,871 participants in the UK Biobank study. Finally, genetic correlation analyses and enrichment analyses were performed with genome-wide association study (GWAS) summary statistics. Results: Familial coaggregation analyses revealed decreasing odds of concurrence of stress-related disorders and autoimmune disease with descending kinship or genetic relatedness between pairs of relatives; adjusted odds ratios were 1.51 (95% CI=1.09–2.07), 1.28 (95% CI=0.97–1.68), 1.16 (95% CI=1.14–1.18), and 1.01 (95% CI=0.98–1.03) for monozygotic twins, dizygotic twins, full siblings, and half cousins, respectively. Statistically significant positive associations were observed between PRSs of stress-related disorders and autoimmune disease, as well as between PRSs of autoimmune disease and stress-related disorders. GWAS summary statistics revealed a genetic correlation of 0.26 (95% CI=0.14–0.38) between these two phenotypes and identified 10 common genes and five shared functional modules, including one module related to G-protein–coupled receptor pathways. Similar analyses performed for PTSD and specific autoimmune diseases (e.g., autoimmune thyroid disease) largely recapitulated the results of the main analyses. Conclusions: This study demonstrated familial coaggregation, genetic correlation, and common biological pathways between stress-related disorders and autoimmune disease.

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.

Epidemiology and treatment of myasthenia gravis: a retrospective study using a large insurance claims dataset in Germany

Myasthenia gravis (MG) is a rare, chronic autoimmune disease with symptoms of fluctuating muscular weakness and fatigability. The aim of this retrospective cohort study was to estimate the prevalence and incidence of MG in Germany, and to understand the burden of disease and treatment patterns, based on anonymized German claims data. Two patient samples were identified: (1) incident MG patients with newly onset disease between 2015 and 2019, and (2) prevalent MG patients in 2019. In total, 775 incident MG patients with a mean age of 66.9 years; and 1,247 prevalent MG patients with a mean age of 68.6 years were included. The prevalence for Germany was estimated to be 39.3/100,000 on 31/12/2019; the incidence in 2019 was 4.6 cases/100,000 persons. The 12-month mortality was 5.7. For 31.5% of the incident patients, no MG treatment was observed in the first year after the index date. Of all incident patients, 29.9% experienced an exacerbation, and 6.7% a myasthenic crisis during the observation. Our study indicates that a substantial proportion of MG patients remains untreated. Many MG patients still experience exacerbations / MG crises. MG seems to be associated with an excess mortality in comparison to the general non-MG population.

Familial autoimmunity in patients with idiopathic inflammatory myopathies

BACKGROUND

Familial associations can be indicators of shared genetic susceptibility between two diseases. Previous data on familial autoimmunity in patients with idiopathic inflammatory myopathies (IIM) are scarce and inconsistent.

OBJECTIVES

To investigate which autoimmune diseases (ADs) may share genetic susceptibility with IIM, we examined the familial associations between IIM and different ADs.

METHODS

In this Swedish population-based family study, we assembled 7615 first-degree relatives (FDRs) of 1620 patients with IIM and 37,309 relatives of 7797 matched individuals without IIM. Via register linkages, we ascertained rheumatoid arthritis, other rheumatic inflammatory diseases (RIDs), multiple sclerosis, inflammatory bowel diseases (IBD), type 1 diabetes mellitus, autoimmune thyroid diseases (AITD), coeliac disease (CeD) and myasthenia gravis among the FDRs. We estimated the familial association between IIM and each AD using conditional logistic regression and performed subgroup analyses by kinship.

RESULTS

Patients with IIM had significantly higher odds of having ≥1 FDR affected by other RIDs (adjusted odds ratio [aOR] = 1.40, 95% confidence interval [CI] 1.11-1.78) and greater odds of having ≥2 FDRs affected by CeD (aOR = 3.57, 95% CI 1.28-9.92) compared to the individuals without IIM. In the analyses of any FDR pairs, we observed familial associations for other RIDs (aOR = 1.34, 95% CI 1.14-1.56), IBD (aOR = 1.20, 95% CI 1.02-1.41), AITD (aOR = 1.10, 95% CI 1.02-1.19) and CeD (aOR = 1.37, 95% CI 1.08-1.74) while associations for other ADs were not statistically significant.

CONCLUSION

The observed familial associations may suggest that IIM shares genetic susceptibility with various ADs, information that may be useful for clinical counselling and guiding future genetic studies of IIM.

Comorbidities in Patients with Vitiligo: A Systematic Review and Meta-Analysis

Vitiligo has been reported to be associated with a variety of diseases, but it has not been systematically reviewed. Therefore, we aimed to identify prevalent diseases in patients with vitiligo and quantify their associations compared with those in healthy controls. A comprehensive search of MEDLINE and EMBASE from the inception to June 2022 was conducted. Observational studies on prevalent diseases in patients with vitiligo compared with those in healthy controls were included, whereas studies limited to pediatrics or providing only laboratory results were excluded. A total of 78 studies were eligible for analyses. Patients with vitiligo showed higher risks of having comorbid autoimmune and connective tissue diseases, including alopecia areata (OR = 2.63, 95% confidence interval [CI] = 2.50‒2.78), discoid lupus erythematosus (OR = 2.54, 95% CI = 1.74‒3.72), Sjogren's syndrome (OR = 2.50, 95% CI = 1.98‒3.16), myasthenia gravis (OR = 2.30, 95% CI = 1.74‒3.02), systemic lupus erythematosus (OR = 1.96, 95% CI = 1.52‒2.52), and rheumatoid arthritis (OR = 1.82, 95% CI = 1.55‒2.15). Thyroid diseases, diabetes mellitus, metabolic syndrome, sensorineural hypoacusis, and ophthalmic abnormalities were also more prevalent in patients with vitiligo. In conclusion, vitiligo is associated with various systemic diseases. Physicians should evaluate and manage potential comorbid conditions in patients with vitiligo.

Clinical characteristics of myasthenia gravis (MG) patients developing other autoimmune diseases after thymectomy from one single center cohort

BACKGROUND

Myasthenia gravis (MG) patients are reported to have a high risk of other autoimmune diseases (ADs), and thymectomy may increase the risk further. A cohort of MG patients in which thymectomy was performed were investigated to analyze the prevalence, types and features of the new onset ADs.

METHODS

Consecutive patients with MG who underwent thymectomy at Beijing Hospital between January 2012 and August 2021 were retrospectively enrolled. Patients with a postoperative follow-up period shorter than a year or incomplete clinical records were excluded. Clinical and follow-up data were collected. Statistical analyses were performed using SPSS version 22.0.

RESULTS

A total of 445 patients were included in this study. The median follow-up period was 72 months (range, 12-135 months). A total of 63 (14.2%) MG patients had concurrent ADs. The incidence rate was higher than the background prevalence of population (5%), and also higher than that of a former Chinese MG cohort (11.6%). A total of 47 patients (10.6%) were diagnosed with ADs before thymectomy, and 19 (4.3%) developed a new AD after thymectomy. The most common types of new onset ADs after thymectomy were Hashimoto's thyroiditis and rheumatoid arthritis (RA), which were different from those before thymectomy (hyperthyroidism and Hashimoto's thyroiditis). The incidence rate of new onset RA (1.35%) was higher than the frequency of RA before thymectomy (0.45%), and also higher than the incidence rate in a Chinese MG cohort (0.5%). There was a higher proportion of female patients (p = 0.026) with postoperative ADs. A younger age at operation may increase the risk of nonthymoma MG patients (p = 0.040) developing ADs. The postoperative treatment effect of MG was similar between patients with and without new onset ADs (p > 0.05).

CONCLUSIONS

We observed a higher incidence rate of autoimmune diseases, especially rheumatoid arthritis, in MG patients after thymectomy. The most common types of ADs after thymectomy were different from those before thymectomy. New onset ADs tended to occur in female and young nonthymoma MG patients. The postoperative effect of MG was not related with the new occurrence of ADs.

Efficacy and Safety of Rituximab for New-Onset Generalized Myasthenia Gravis: The RINOMAX Randomized Clinical Trial

Importance

Rituximab is a third-line option for refractory generalized myasthenia gravis (MG) based on empirical evidence, but its effect in new-onset disease is unknown.

Objective

To investigate the efficacy and safety of rituximab compared with placebo as an add-on to standard of care for MG.

Design, Setting, and Participants

This randomized, double-blind, placebo-controlled study took place throughout 48 weeks at 7 regional clinics in Sweden. Key inclusion criteria were age older than 18 years, onset of generalized symptoms within 12 months or less, and a Quantitative Myasthenia Gravis (QMG) score of 6 or more. Patients were screened from October 20, 2016, to March 2, 2020. Key exclusion criteria included pure ocular MG, suspected thymoma, previous thymectomy, and prior noncorticosteroid immunosuppressants or high doses of corticosteroids.

Interventions

Participants were randomized 1:1 without stratification to a single intravenous infusion of 500 mg of rituximab or matching placebo.

Main Outcomes and Measures

Minimal disease manifestations at 16 weeks defined as a QMG score of 4 or less with prednisolone, 10 mg or less daily, and no rescue treatment.

Results

Of 87 potentially eligible patients, 25 were randomized to rituximab (mean [SD] age, 67.4 [13.4] years; 7 [28%] female) and 22 to placebo (mean [SD] age, 58 [18.6] years; 7 [32%] female). Compared with placebo, a greater proportion with rituximab met the primary end point; 71% (17 of 24) in the rituximab group vs 29% (6 of 21) in the placebo group (Fisher exact test P = .007; probability ratio, 2.48 [95% CI, 1.20-5.11]). Secondary end points, comparing changes in Myasthenia Gravis Activities of Daily Living and Myasthenia Gravis Quality of Life at 16 weeks with QMG at 24 weeks did not differ between groups with censoring for rescue treatment (per-protocol analysis) but were in favor of active treatment when rescue treatment was taken into account by worst rank imputation (post hoc analysis). Rescue treatments were also more frequent in the placebo arm (rituximab: 1 [4%]; placebo, 8 [36%]). One patient in the placebo arm had a myocardial infarction with cardiac arrest and 1 patient in the active arm experienced a fatal cardiac event.

Conclusions and Relevance

A single dose of 500 mg of rituximab was associated with greater probability of minimal MG manifestations and reduced need of rescue medications compared with placebo. Further studies are needed to address long-term benefit-risk balance with this treatment.

Trial Registration

ClinicalTrials.gov Identifier: NCT02950155.

Cross-syndrome: myasthenia gravis and the demyelinating diseases of the central nervous system combination. Systematic literature review and case reports

Nowadays the problem of comorbidity is still relevant. In this review, we describe clinical cases of the disease of the neuromuscular junction (myasthenia gravis (MG) generalized form) and the demyelinating disease of the central nervous system (DD CNS) (multiple sclerosis, neuromyelitis optica spectrum disorder (NMOSD), etc.) combinations registered in our practice with precise pathogenetic analysis. Although the number of the described associations is growing every year, the exact development mechanisms of this cross syndrome as well as the nature of the association between the discussed autoimmune diseases remain unknown. At the beginning of both disorders there is a considerable loss of auto tolerance of the immune system and, as a result, an increased response from autoreactive T-lymphocytes to the structures of the nervous system: brain cells and neuromuscular synapses. There are three main theories for comorbidity: initial predisposition, direct case relationship with disease-modifying therapy (DMT) application, and coincidence. It is known that early diagnostics of MG and timely administration of necessary adequate treatment reduce the risk of process generalization and lead to a decline in mortality. Therefore, the offer to examine MS patients with atypical symptoms for possible MG identification seems very rational. Similarly, MG patients having uncharacteristic symptoms that can be indicative of other autoimmune nervous system diseases also demand special diagnostics. Considering the presence of similar pathogenetic links, several authors propose a possibility of a new nosological unit establishment, including described comorbidity.

Rheumatoid arthritis and myasthenia gravis: a case-based review of the therapeutic options

Introduction

Myasthenia gravis is an autoimmune disease affecting the neuromuscular junction, often associated with other autoimmune diseases, including rheumatoid arthritis. Patients with rheumatoid arthritis present an increased prevalence of myasthenia gravis compared to the general population. While these two diseases share some therapeutic options, such as glucocorticoids, methotrexate, and rituximab, there are no guidelines for treating concomitant disease. We aim to review the available evidence and to discuss the efficacy and safety of the therapeutic options in patients with rheumatoid arthritis associated with myasthenia gravis.

Method

We described three patients with rheumatoid arthritis associated with myasthenia gravis and we performed a systematic review of the associated literature.

Results

A 48-year-old man and two women (48 and 55 years old) with concomitant diagnoses of active rheumatoid arthritis and well-controlled myasthenia gravis are described. They were treated with methotrexate, leflunomide, upadacitinib, and adalimumab. None of them experienced changes in their myasthenic symptoms. We found 9 additional cases from our literature review. Methotrexate, rituximab, upadacitinib, diphenyl sulfone, auranofin, and loxoprofen sodium did not show an impact on the seven patients with previously well-controlled myasthenia. Glucocorticoids, methotrexate, and rituximab proved effective in active myasthenia gravis and arthritis. Conflicting data emerged for Tumor-necrosis factor inhibitors.

Conclusions

Although the available evidence remains scarce, we consider glucocorticoids, methotrexate, and rituximab as safe and effective options. The role of tumor-necrosis factor inhibitors remains uncertain. Eventually, Janus Kinase inhibitors are a novel interesting option for these patients.

Key Points • To date, the only evidence on the treatment of patients with rheumatoid arthritis and concomitant myasthenia gravis derives from case reports. • Based on the review of the available case reports and on the cases we described, we consider glucocorticoids, methotrexate, and rituximab as safe and effective options, while the role of Tumor-necrosis factor inhibitors remains uncertain. • Based on the cases we described, Janus Kinase inhibitors are a novel interesting option for patients with concomitant rheumatoid arthritis and myasthenia gravis.

Comorbid Autoimmune Diseases in Patients With Myasthenia Gravis: A Retrospective Cross-Sectional Study of a Chinese Cohort

Introduction: The phenomenon of coexisting autoimmune diseases (ADs) in patients with myasthenia gravis (MG) has attracted considerable attention. However, few studies have investigated the burden and potential clinical associations of ADs in Chinese MG cohorts.

Methods: In this retrospective cross-sectional study, we reviewed the records of 1,132 patients with MG who were admitted to Huashan Hospital Fudan University from August 2013 to August 2020. Patients were excluded if they had incomplete medical records (n = 336).

Results: Comorbid ADs were found in 92 of 796 Chinese patients with MG (11.6%), among which, hyperthyroidism (6.7%), hypothyrosis (2.6%), and vitiligo (0.8%) were predominant. Patients with MG with ADs were predominantly female, younger at the onset of MG symptoms, and had a lower frequency of thymoma. Compared to the general population, we found a significantly higher percentage of hyperthyroidism (8.5-fold increase, p < 0.001), hypothyrosis (2.6-fold increase, p < 0.001), vitiligo (1.3-fold increase, p < 0.001), rheumatoid arthritis (1.4-fold increase, p < 0.001), immune thrombocytopenic purpura (193.1-fold increase, p < 0.001), autoimmune hemolytic anemia (7.4-fold increase, p < 0.001), autoimmune hepatitis (5.1-fold increase, p < 0.001), and polymyositis (11.5-fold increase, p < 0.001) in patients with MG with ADs. Patients with MG with ADs presented a lower proportion of previous history of MC (0 vs. 5.6%, p < 0.05) than those without ADs. The proportion of MGFA Class I at onset in patients with MG with ADs was significantly higher than that in patients with MG without ADs (77.0 vs. 52.7%, p < 0.05). The proportion of MuSK-positive in patients with MG with ADs was significantly lower than that in patients with MG without ADs (0 vs. 4.8%, p < 0.05).

Conclusion: In conclusion, we observed a higher frequency of concurrent ADs in a Chinese MG cohort. Furthermore, MG combined with ADs tended to have mild clinical presentation.

Patient-Reported Symptom Severity in a Nationwide Myasthenia Gravis Cohort: Cross-sectional Analysis of the Swedish GEMG Study

BACKGROUND AND OBJECTIVES

To describe myasthenia gravis activities of daily living (MG-ADL) in relation to clinical characteristics in a large Swedish nationwide cohort.

METHODS

In a cross-sectional prevalence cohort study, the Genes and Environment in Myasthenia Gravis study, performed from November 2018 through August 2019, patients with myasthenia gravis (MG) were invited to submit an extensive 106-item life environment questionnaire, including the MG-ADL score. Patients were classified into early-onset MG (EOMG, <50 years), late-onset MG (LOMG, ≥50 years), or thymoma-associated MG (TAMG). Comparisons of disease-specific characteristics were made between subgroups, sexes, and different MG-ADL scores.

RESULTS

A total of 1,077 patients were included, yielding a 74% response rate: 505 (47%) were classified as EOMG, 520 (48%) LOMG, and 45 (4%) TAMG. Mean age at inclusion was 64.3 years (SD 15.7) and mean disease duration was 14.6 years (SD 14.0). Complete MG-ADL scores (n = 1,035) ranged from 0p to 18p, where 26% reported a score of 0p. Higher MG-ADL scores were associated with female sex, obesity, and diagnostic delay (odds ratio [OR] 1.62, 1.72, and 1.69; p adj = 0.017, 0.013, and 0.008) and inversely correlated with high educational attainment (OR 0.59; p adj = 0.02), but not with age at inclusion, disease subtype, or disease duration. Almost half of the population (47%) reported MG-ADL ≥3p, corresponding to an unsatisfactory symptom state.

DISCUSSION

In this nationwide study, comprising more than 40% of the prevalent MG population in Sweden, almost half of the patients reported current disease symptoms associated with an unsatisfactory symptom state, indicating the need for improved treatment options.

Comorbidities worsen the prognosis of generalized myasthenia gravis post-thymectomy

BACKGROUND

The effect of comorbidities on the prognosis of myasthenia gravis (MG) remains unclear. In particular, the role of other autoimmune diseases (AD) is controversial.

METHODS

In this retrospective single-center cohort study, we investigated 154 consecutive generalized thymectomized MG patients, with a mean follow-up time of 8.6 (±5.0) years post-thymectomy. Comorbidities diagnosed at any timepoint were retrieved from medical records and Charlson comorbidity index (CCI) scores were calculated. Patients were categorized into subgroups MG alone (n = 45) and MG with any comorbidity (n = 109); the latter was further categorized into MG with other ADs (n = 33) and MG with non-AD comorbidities (n = 76). The endpoints analyzed were complete stable remission (CSR), minimal need for medications, and need for in-hospital treatments.

RESULTS

CSR was more frequent in MG alone than in MG with any comorbidity group (26.7% vs 8.3%, p = 0.004). Minimal need for medication was reached more often in the MG alone than in the MG with non-AD comorbidities group (p = 0.047). Need for in-hospital treatments was lower in the MG alone group than in MG patients with any comorbidity (p = 0.046). Logistic regression analysis revealed that lower CCI scores increased the likelihood of CSR (p = 0.033). Lower CCI scores were more prevalent both in patients with minimal need for medication and in patients who did not need in-hospital treatments (p < 0.001).

CONCLUSIONS

Patients with generalized MG and comorbidities have a poorer prognosis than patients with MG alone during almost 9 years follow-up after thymectomy. AD comorbidities appeared not to translate into a higher risk compared to other comorbidities.

Next-Generation Sequencing Identifies Extended HLA Class I and II Haplotypes Associated With Early-Onset and Late-Onset Myasthenia Gravis in Italian, Norwegian, and Swedish Populations

Genetic susceptibility to myasthenia gravis (MG) associates with specific HLA alleles and haplotypes at the class I and II regions in various populations. Previous studies have only examined alleles at a limited number of HLA loci that defined only broad serotypes or alleles defined at the protein sequence level. Consequently, genetic variants in noncoding and untranslated HLA gene segments have not been fully explored but could also be important determinants for MG. To gain further insight into the role of HLA in MG, we applied next-generation sequencing to analyze sequence variation at eleven HLA genes in early-onset (EO) and late-onset (LO) non-thymomatous MG patients positive for the acetylcholine receptor (AChR) antibodies and ethnically matched controls from Italy, Norway, and Sweden. For all three populations, alleles and haplotype blocks present on the ancestral haplotype AH8.1 were associated with risk in AChR-EOMG patients. HLA-B*08:01:01:01 was the dominant risk allele in Italians (OR = 3.28, P = 1.83E-05), Norwegians (OR = 3.52, P = 4.41E-16), and in Swedes HLA-B*08:01 was the primary risk allele (OR = 4.24, P <2.2E-16). Protective alleles and haplotype blocks were identified on the HLA-DRB7, and HLA-DRB13.1 class II haplotypes in Italians and Norwegians, whereas in Swedes HLA-DRB7 exhibited the main protective effect. For AChR-LOMG patients, the HLA-DRB15.1 haplotype and associated alleles were significantly associated with susceptibility in all groups. The HLA-DR13-HLA-DR-HLA-DQ haplotype was associated with protection in all AChR-LOMG groups. This study has confirmed and extended previous findings that the immunogenetic predisposition profiles for EOMG and LOMG are distinct. In addition, the results are consistent with a role for non-coding HLA genetic variants in the pathogenesis of MG.

Disappearance of Anti-Thyroid Autoantibodies following Thymectomy in Patients with Myasthenia Gravis

OBJECTIVES

The thymus plays a central role in immune tolerance, which prevents autoimmunity. Myasthenia gravis (MG) is commonly associated with thymoma or thymus hyperplasia, and it can coexist with autoimmune thyroid diseases. However, the role of the thymus in thyroid autoimmunity remains to be clarified, which we investigated here.

STUDY DESIGN

The study design entailed the inclusion of consecutive MG patients and the measurement of anti-thyroid autoantibodies at baseline and, limited to autoantibody-positive patients, also at 24 and 48 weeks. One hundred and seven MG patients were studied. The main outcome measure was the behaviour of anti-thyroglobulin autoantibodies (TgAbs) and anti-thyroperoxidase autoantibodies (TPOAbs) over time in relation to thymectomy.

RESULTS

Serum TgAbs and/or TPOAbs were detected in ∼20% of patients in the absence of thyroid dysfunction. The prevalence of positive serum TgAbs and/or TPOAbs decreased significantly (p = 0.002) over the follow-up period in patients who underwent thymectomy, but not in patients who were not thymectomized. When the analysis was restricted to TgAbs or TPOAbs, findings were similar. On the same line, there was a general trend towards a reduction in the serum concentrations of anti-thyroid autoantibodies in patients who underwent thymectomy, which was significant for TPOAbs (p = 0.009).

CONCLUSIONS

Our findings suggest a role of the thymus in the maintenance of humoral thyroid autoimmunity.

Association Between Myasthenia Gravis and Systemic Lupus Erythematosus as a Comorbid State

Systemic lupus erythematosus (SLE) and myasthenia gravis (MG) are autoimmune states which have presentational similitude. Both conditions test serologically positive for anti-nuclear antibodies and require exceptional differential diagnostic acumen to segregate one from the other. The hypothesized factors provoking these diseases may be immunological, genetic, hormonal, or environmental and can be better understood by large-scale controlled epidemiological studies. Biochemical factors such as variation in CXC (an α chemokine subfamily), CXCL13, and granulocyte-macrophage colony-stimulating factor levels are assumed to play a pivotal role in the pathogenesis of SLE and MG; however, further studies are required to understand their exact mechanism and effect on the underlying autoimmune diseases. Following this, another precipitating factor for this overlap is believed to be thymectomy which is performed to eliminate MG symptoms. Although thymectomy is the effective treatment modality in MG patients, other findings and data support the view that this procedure may lead to the development of other autoimmune states such as SLE. It is evident from previously published data and case reports that patients with one autoimmune disease who underwent thymectomy contracted SLE and became more susceptible to other autoimmune diseases compared to the general population. Post-thymectomy follow-up of patients provides us with mechanistic clues for understanding the development of SLE-MG overlap; hence, in MG patients who have undergone thymectomy, any clinical and immune serological SLE suspicion should be carefully evaluated.

Comparison Between Rituximab Treatment for New-Onset Generalized Myasthenia Gravis and Refractory Generalized Myasthenia Gravis

Importance

Use of biologic agents in generalized myasthenia gravis is generally limited to therapy-refractory cases; benefit in new-onset disease is unknown.

Objective

To assess rituximab in refractory and new-onset generalized myasthenia gravis and rituximab vs conventional immunotherapy in new-onset disease.

Design, Setting, and Participants

A retrospective cohort study with prospectively collected data was conducted on a county-based community sample at Karolinska University Hospital, Stockholm, Sweden. Participants included 72 patients with myasthenia gravis, excluding those displaying muscle-specific tyrosine kinase antibodies, initiating rituximab treatment from January 1, 2010, to December 31, 2018, and patients with new-onset disease initiating conventional immunotherapy from January 1, 2003, to December 31, 2012, with 12 months or more of observation time. The present study was conducted from March 1, 2019, to January 31, 2020.

Exposures

Treatment with low-dose rituximab (most often 500 mg every 6 months) or conventional immunosuppressants.

Main Outcomes and Measures

Time to remission (main outcome) as well as use of rescue therapies or additional immunotherapies and time in remission (secondary outcomes).

Results

Of the 72 patients included, 31 patients (43%) were women; mean (SD) age at treatment start was 60 (18) years. Twenty-four patients had received rituximab within 12 months of disease onset and 48 received rituximab at a later time, 34 of whom had therapy-refractory disease. A total of 26 patients (3 [12%] women; mean [SD] age, 68 [11] years at treatment start) received conventional immunosuppressant therapy. Median time to remission was shorter for new-onset vs refractory disease (7 vs 16 months: hazard ratio [HR], 2.53; 95% CI, 1.26-5.07; P = .009 after adjustment for age, sex, and disease severity) and for rituximab vs conventional immunosuppressant therapies (7 vs 11 months: HR, 2.97; 95% CI, 1.43-6.18; P = .004 after adjustment). In addition, fewer rescue therapy episodes during the first 24 months were required (mean [SD], 0.38 [1.10] vs 1.31 [1.59] times; mean difference, -1.26; 95% CI, -1.97 to -0.56; P < .001 after adjustment), and a larger proportion of patients had minimal or no need of additional immunotherapies (70% vs 35%; OR, 5.47; 95% CI, 1.40-21.43; P = .02 after adjustment). Rates of treatment discontinuation due to adverse events were lower with rituximab compared with conventional therapies (3% vs 46%; P < .001 after adjustment).

Conclusions and Relevance

Clinical outcomes with rituximab appeared to be more favorable in new-onset generalized myasthenia gravis, and rituximab also appeared to perform better than conventional immunosuppressant therapy. These findings suggest a relatively greater benefit of rituximab earlier in the disease course. A placebo-controlled randomized trial to corroborate these findings is warranted.

Zilucoplan: An Investigational Complement C5 Inhibitor for the Treatment of Acetylcholine Receptor Autoantibody-Positive Generalized Myasthenia Gravis

INTRODUCTION

Generalized myasthenia gravis (gMG) is an autoimmune disorder in which pathogenic autoantibodies damage the neuromuscular junction, causing disabling or life-threatening muscle weakness. Most treatments nonspecifically inhibit aspects of the immune system, do not directly address the causal mechanisms of tissue damage, and often have side-effect profiles that negatively impact patients. Understanding of the central pathogenic role of the complement cascade in gMG is advancing, and a new complement-targeting treatment is under investigation.

AREAS COVERED

We provide an overview of gMG etiology, the complement cascade, current treatments, and the investigational gMG therapy zilucoplan. Zilucoplan is a small, subcutaneously administered, macrocyclic peptide that inhibits cleavage of complement component C5 and the subsequent formation of the membrane attack complex.

EXPERT OPINION

In a randomized, double-blind, placebo-controlled, phase 2 clinical trial, zilucoplan demonstrated clinically meaningful complement inhibition in patients with acetylcholine receptor-positive gMG. Zilucoplan, a first-of-its-kind cyclic peptide targeting C5, appears to be a therapeutic option for the treatment of gMG based on available pharmacokinetic/pharmacodynamic data and phase 1 and 2 efficacy, safety, and tolerability data with limited long-term follow-up. Zilucoplan use earlier in the treatment paradigm would be suitable in this population should phase 3 efficacy and safety data be equally favorable.

Safety and effectiveness of eculizumab in Japanese patients with generalized myasthenia gravis: interim analysis of post-marketing surveillance

BACKGROUND

Eculizumab, a humanized monoclonal antibody targeted to terminal complement protein C5, is approved in Japan for treatment of patients with anti-acetylcholine receptor antibody-positive (AChR+) generalized myasthenia gravis (gMG) whose symptoms are difficult to control with high-dose intravenous immunoglobulin (IVIg) therapy or plasmapheresis.

METHODS

This interim analysis of mandatory post-marketing surveillance in Japan assessed the safety and effectiveness of eculizumab at 26 weeks after treatment initiation in patients with AChR+ gMG.

RESULTS

Data were available for 40 adult patients in Japan [62.5% (25/40) female; mean age at eculizumab initiation, 51.0 years]. Fifteen patients had a history of thymoma. Six patients were excluded from the effectiveness analysis set due to participation in the open-label extension part of the phase III, randomized, double-blind, placebo-controlled REGAIN study [ClinicalTrials.gov identifier: NCT02301624]. After 26 weeks' follow up, 32 patients (80%) were continuing eculizumab treatment. Adverse drug reactions were reported by seven patients [most frequently headache (n = 3)]. One death was reported during eculizumab treatment (relationship unclear as determined by the treating physician) and there was one death 45 days after the last dose (considered unrelated). No meningococcal infections were reported. Mean (standard deviation) changes from baseline in Myasthenia Gravis-Activities of Daily Living (MG-ADL) and Quantitative Myasthenia Gravis (QMG) scores were -3.7 (2.61) (n = 27) and -5.6 (3.50) (n = 26), respectively, at 12 weeks, and -4.3 (2.72) (n = 26) and -5.6 (4.02) (n = 24), respectively, at 26 weeks. Improvements in MG-ADL and QMG scores were generally similar in patients with/without a history of thymoma. Frequency of IVIg use decreased following eculizumab initiation.

CONCLUSION

In a real-world setting, eculizumab was effective and well tolerated for the treatment of AChR+ gMG in adult Japanese patients whose disease was refractory to IVIg or plasmapheresis. These findings are consistent with the efficacy and safety results from the global phase III REGAIN study of eculizumab.

Thymectomy in Juvenile Myasthenia Gravis Is Safe Regarding Long Term Immunological Effects

Thymectomy is an established treatment in adult MG and also recommended for the treatment of post-pubertal onset juvenile MG. Whether the youngest children should be thymectomized is still debated. Signs of premature aging of the immune system have been shown in studies on early perioperative thymectomy in children with congenital heart defect. In this retrospective cohort study the objective was to investigate the long-term effects of treatment related thymectomy on T cell subsets and T cell receptor rearrangement excision circles (TRECs) in peripheral blood of juvenile myasthenia gravis (MG) patients, as well as clinical occurrence of autoimmune disorders, malignancies and infectious diseases. Forty-seven patients with onset of myasthenia gravis before the age of 19 years were included; 32 (68.1%) had been thymectomized and 15 (31.8%) had not. They were studied at varying times after thymectomy (7–26 years). We found a significant lower number of naïve helper T cells (CD4+CD45RA+) with an increased proportion of memory helper T cells (CD4+CD45RO+), and a significant lower number of naïve cytotoxic T cells (CD8+CD27+CD28+) in the thymectomized patients. In addition they showed a significant reduction in the number of TRECs and proportion of recent thymic emigrants (RTE) compared to non-thymectomized patients. In none of them an increased frequency of malignancies or infections was found. Our findings indicate a premature aging of the immune system after thymectomy in juvenile MG, but associated clinical consequences could not be verified.

Cancer in myasthenia gravis subtypes in relation to immunosuppressive treatment and acetylcholine receptor antibodies: A Swedish nationwide register study

BACKGROUND AND PURPOSE

The potentially increased risk of extrathymic cancers in myasthenia gravis (MG) remains uncertain. We present the occurrence of extrathymic cancer diagnoses in different MG subgroups.

METHODS

We conducted a nationwide Swedish register-based cohort study, including patients who had their first MG diagnosis or first prescription of acetylcholine esterase inhibitors between the years 2006 and 2018. Timing and subtypes of cancer diagnosis in relation to MG as well as corticosteroid-sparing immunosuppressants (CSISs) were identified from national patient, cancer and drug registers.

RESULTS

In the study population of 2812 MG patients, 92 had juvenile MG (3%), 632 had early-onset MG (23%), 1968 had late-onset MG (LOMG; 70%) and 120 patients had thymoma-associated MG (TAMG; 4%). Extrathymic cancers were observed in 630 patients (22.4%). Skin cancer and cancer in the male genital organs were most common (N = 138, respectively), followed by cancers in the female genital organs (N = 103), digestive organs (N = 90) and breast (N = 80). Patients with TAMG (29.2%) and LOMG (28.4%) had the highest occurrence of extrathymic cancer. Cancer frequency was comparable between acetylcholine receptor antibody seropositive and seronegative patients. Two or more CSIS prescriptions significantly increased the frequency of cancer, especially cancers in the digestive organs (p = 0.0026), male genital organs (p = 0.0037) and skin (p < 0.0001).

CONCLUSIONS

Most extrathymic cancer types in MG were observed in TAMG and LOMG patients, and there was a clear correlation between CSIS exposure and cancer risk. This study sheds light on extrathymic cancers also in non-thymoma MG.

Thymic Hyperplasia with Lymphoepithelial Sialadenitis (LESA)-Like Features: Strong Association with Lymphomas and Non-Myasthenic Autoimmune Diseases

Thymic hyperplasia (TH) with lymphoepithelial sialadenitis (LESA)-like features (LESA-like TH) has been described as a tumor-like, benign proliferation of thymic epithelial cells and lymphoid follicles. We aimed to determine the frequency of lymphoma and autoimmunity in LESA-like TH and performed retrospective analysis of cases with LESA-like TH and/or thymic MALT-lymphoma. Among 36 patients (21 males) with LESA-like TH (age 52 years, 32-80; lesion diameter 7.0 cm, 1-14.5; median, range), five (14%) showed associated lymphomas, including four (11%) thymic MALT lymphomas and one (3%) diffuse large B-cell lymphoma. One additional case showed a clonal B-cell-receptor rearrangement without evidence of lymphoma. Twelve (33%) patients (7 women) suffered from partially overlapping autoimmune diseases: systemic lupus erythematosus (n = 4, 11%), rheumatoid arthritis (n = 3, 8%), myasthenia gravis (n = 2, 6%), asthma (n = 2, 6%), scleroderma, Sjögren syndrome, pure red cell aplasia, Grave's disease and anti-IgLON5 syndrome (each n = 1, 3%). Among 11 primary thymic MALT lymphomas, remnants of LESA-like TH were found in two cases (18%). In summary, LESA-like TH shows a striking association with autoimmunity and predisposes to lymphomas. Thus, a hematologic and rheumatologic workup should become standard in patients diagnosed with LESA-like TH. Radiologists and clinicians should be aware of LESA-like TH as a differential diagnosis for mediastinal mass lesions in patients with autoimmune diseases.

The epidemiology of myasthenia gravis

Neuromuscular junction (NMJ) disorders include several dysfunctions that ultimately lead to muscle weakness. Myasthenia gravis (MG) is the most prevalent NMJ disorder with a highly polymorphic clinical presentation and many different faces. Being an autoimmune disease, MG correlates with the presence of detectable antibodies directed against the acetylcholine receptor, muscle-specific kinase, lipoprotein-related protein 4, agrin, titin, and ryanodine in the postsynaptic membrane at the NMJ. MG has become a prototype serving to understand both autoimmunity and the function of the NMJ better. The aim of this review is to synthesize some of the epidemiological data available. Epidemiological data regarding MG are important for postulating hypotheses regarding its etiology and facilitating the description of MG subtypes. Thus, adequate documentation through broad databases is essential. The incidence and prevalence of MG reported around the globe have been rising steadily and consistently over the past decades. Ethnic aspects, gender-related differences, and environmental risk factors have been described, implying that these might contribute to a specific phenotype, further suggesting that MG may be considered an umbrella term that covers several clinical entities.

Concomitant Immunosuppressive Therapy Use in Eculizumab-Treated Adults With Generalized Myasthenia Gravis During the REGAIN Open-Label Extension Study

Introduction: Chronic, broad-spectrum immunosuppressive therapy (IST) can be associated with side effects in many people with generalized myasthenia gravis (gMG), and treatment guidelines recommend that the IST dose be tapered once patients achieve a stable treatment response. We therefore examined IST use in eculizumab-treated patients with refractory gMG.

Methods: The REGAIN open-label extension (OLE) enrolled 117 adults with refractory anti-acetylcholine receptor antibody-positive gMG who had completed the 6-month, randomized, double-blind, placebo-controlled REGAIN study of eculizumab. Eligible patients had received ≥2 ISTs for ≥1 year or ≥1 IST with intravenous immunoglobulin or plasma exchange ≥4 times in 1 year, without symptom control. During REGAIN, changes in concomitant MG therapies were not permitted; during the OLE, they were permitted at the investigators' discretion. Participants received eculizumab 1,200 mg every 2 weeks for up to 4 years; concomitant prednisone and related corticosteroids (PRED), azathioprine (AZA), and mycophenolate mofetil (MMF) use was recorded. Changes in MG Activities of Daily Living and Quantitative MG total scores, MG exacerbations, and adverse events were also recorded.

Results: At last OLE assessment, 88.0% (103/117) of participants were using ≥1 IST vs. 98.3% (115/117) at OLE baseline. During the OLE, 76.9% (90/117) of patients experienced a total of 719 IST changes. Almost half of participants [48.7% (57/117)] stopped or decreased ≥1 IST owing to MG symptom improvement, representing 38.9% (280/719) of all changes. In patients who decreased and/or stopped ≥1 IST, mean daily doses of PRED, AZA, and MMF decreased between OLE baseline and last assessment by 60.8% [standard deviation (SD), 28.07; P < 0.0001], 89.1% (SD, 25.77; P < 0.0001), and 56.0% (SD, 32.99; P < 0.0001), respectively. Improved clinical outcomes were observed with eculizumab regardless of IST changes during the OLE, and eculizumab's safety profile was similar in patients who used PRED, AZA, and MMF.

Conclusions: Use of ISTs by patients with previously refractory gMG decreased during eculizumab treatment in the REGAIN OLE. Clinical improvements with eculizumab were maintained by patients in all groups, including those who decreased and/or stopped concomitant ISTs.

Trial registration:www.clinicaltrials.gov: NCT01997229, NCT02301624.

Coexistence of anti-MuSK antibody-positive myasthenia gravis and rheumatoid arthritis

Background

Rheumatoid arthritis (RA) is an autoimmune disease characterized with symmetric synovitis and occasional extra articular involvement; also, some neurologic disorders can be observed during the disease course. Myasthenia gravis (MG) is one of them and it is an autoimmune disease of neuromuscular junction. It is caused by autoantibodies against neuromuscular junction proteins: the nicotinic acetylcholine receptor (AChR) and the muscle specific tyrosine kinase (MuSK). Very few studies have reported the associated autoimmune disorders in MuSK-MG. Here, we present the first patient who has MuSK antibody-positive MG gravis and rheumatoid arthritis.

Case presentation

A 53-year-old woman with RA presented with fatigue and fluctuating proximal muscle weakness. Her electroneurophysiological investigation resembled MG. Her AchR antibody level was normal but MuSK antibodies were high. After the acute treatment with plasmapheresis which lead to complete recovery in myasthenic symptoms, she is following with mycophenolate mofetil.

Conclusions

Concomitant autoimmune disorders are common in the population. MG should be considered in patients with an autoimmune disorder and developing new neuromuscular weakness.

Multiple autoimmune syndrome complicating the management of diabetic retinopathy

Purpose

Observations

Conclusion and Importance

Familial associations for Addison's disease and between Addison's disease and other autoimmune diseases

DESIGN

Addison's disease (AD) is a rare autoimmune disease (AID) of the adrenal cortex, present as an isolated AD or part of autoimmune polyendocrine syndromes (APSs) 1 and 2. Although AD patients present with a number of AID co-morbidities, population-based family studies are scarce, and we aimed to carry out an unbiased study on AD and related AIDs.

METHODS

We collected data on patients diagnosed with AIDs in Swedish hospitals and calculated standardized incidence ratios (SIRs) in families for concordant AD and for other AIDs, the latter as discordant relative risks.

RESULTS

The number of AD patients was 2852, which accounted for 0.4% of all hospitalized AIDs. A total of 62 persons (3.6%) were diagnosed with familial AD. The SIR for siblings was remarkably high, reaching 909 for singleton siblings diagnosed before age 10 years. It was 32 in those diagnosed past age 29 years and the risk for twins was 323. SIR was 9.44 for offspring of affected parents. AD was associated with 11 other AIDs, including thyroid AIDs and type 1 diabetes and some rarer AIDs such as Guillain-Barre syndrome, myasthenia gravis, polymyalgia rheumatica and Sjögren's syndrome.

CONCLUSIONS

The familial risk for AD was very high implicating genetic etiology, which for juvenile siblings may be ascribed to APS-1. The adult part of sibling risk was probably contributed by recessive polygenic inheritance. AD was associated with many common AIDs; some of these were known co-morbidities in AD patients while some other appeared to more specific for a familial setting.

Epidemiology of Myasthenia Gravis in Sweden 2006-2016

INTRODUCTION

Reported incidence and prevalence rates of Myasthenia Gravis (MG) vary widely and are assumed to have increased over the last few decades. We conducted a nationwide register-based study on the current incidence and prevalence of MG and MG subgroups in Sweden.

METHODS

Data were acquired from four Swedish Health Registers in order to identify patients with MG. Incidence and prevalence rates were calculated for the years 2006-2016, using population numbers provided by Statistics Sweden.

RESULTS

In 2016, the incidence of MG in Sweden was 2.9 per 100,000 inhabitants (95% CI: 2.5-3.2/100,000) and the crude prevalence was 36.1 per 100,000 inhabitants (95% CI: 34.9-37.3). There was a significant increase in Myasthenia Gravis prevalence from 2006 to 2016. Prevalence rates of all MG subgroups but thymoma-associated MG increased over the same period of time.

CONCLUSIONS

The incidence and prevalence of Myasthenia Gravis have increased over time in Sweden, and the rates are high in comparison with other countries.

Prevalence and risk of thyroid diseases in myasthenia gravis

OBJECTIVES

To estimate the prevalence of thyroid diseases and the cumulative risk of thyroid diseases during a follow-up period after myasthenia gravis (MG) diagnosis compared with non-MG controls.

MATERIALS AND METHODS

We used the Taiwan National Health Insurance Database linked to Registry of Catastrophic Illness database to identify patients with MG. The controls were composed of those who did not have MG and were matched with the MG patients by sex, age, and the index date. We recorded thyroid disease histories before and after the index date.

RESULTS

Our study included 5813 MG patients and 29 065 controls. The prevalence of thyroid diseases in the MG patients at diagnosis was 18.4%, which was nearly 3.9-fold greater than that in the control group. (Odds ratio [OR] 3.895, 95% Confidence interval [CI] 3.574-4.246) After excluding pre-existing thyroid diseases, the incidence of comorbid thyroid diseases was 8.7% in the MG patients and 4% in the control group. The MG patients had a 2.36-fold increased risk of developing thyroid diseases compared to the control group. (crude hazard ratio [HR] 2.360, 95% CI 2.095-2.659) The cumulative probabilities of developing thyroid diseases at 1, 5, and 10 years after the index date were 21.6%, 24.9%, and 28.7%, respectively, in the MG patients, while the cumulative probabilities were 6.5%, 8.8%, and 11.8%, respectively, in control group (log-rank test <0.0001).

CONCLUSIONS

The current population-based study showed a higher prevalence of pre-existing thyroid diseases and a higher cumulative probability of thyroid diseases during follow-up after MG diagnosis than in the general population.

Immune Checkpoint Inhibitor-Induced Myasthenia Gravis

The development of immune checkpoint inhibitors (ICIs) has been a major breakthrough in cancer immunotherapy. The increasing use of ICIs has led to the discovery of a broad spectrum of immune-related adverse events (irAEs). Immune-related myasthenia gravis (irMG) is a rare but life-threatening irAE. In this review, the clinical presentations of irMG are described and the risk of irMG-related mortality is examined using information from relevant studies. In 47 reported cases of irMG with clear causes of mortality, irMG appeared to be a distinct category of neuromuscular disorders and differed from classical MG in terms of its demographic patient characteristics, pathogenesis, serology profile, response to treatment, associated complications, and prognosis. Because of the high mortality of irMG, measures to increase the vigilance of medical teams are necessary to ensure the timely identification of the signs of irMG and early treatment, particularly in the early course of ICI therapy. The diagnostic plans should be comprehensive and include the evaluation of other organ systems, such as the dermatological, gastrointestinal, respiratory, neuromuscular, and cardiovascular systems, in addition to the traditional diagnostic tests for MG. Treatment plans should be individualized on the basis of the extent of organ involvement and clinical severity. Additional therapeutic studies on irMG in the future are required to minimize irAE-related mortality and increase the safety of patients with cancer in the ICI era.

A study of comorbidities in myasthenia gravis

Management of myasthenia gravis (MG) in the presence of comorbidities may be difficult. We report the effect of comorbidities in the outcome of MG. The patients with MG during 1991-2016 were included and evaluated including their demographic variables, clinical findings, Myasthenia Gravis Foundation of America (MGFA) score. The patients were categorized into early onset (≤ 40 years) and late onset (> 40 years) MG. The comorbidities (autoimmune and miscellaneous) and iatrogenic complications were compared between early and late onset, and in good and poor outcome groups. Out of 81 patients with MG, 48 patients had early and 33 late onset. In 71 (88%) patients, comorbidities were present and were autoimmune in 8 (10%) and miscellaneous in all the patients (88%). Iatrogenic complications were present in 54 (67%) patients. Thymectomy was done in 19 patients; 16 had thymoma and 3 thymic hyperplasia. Myasthenic crisis occurred in 28 patients; 5 (18%) had autoimmune and all had miscellaneous comorbidities. The patients with poor outcome had ≥ 2 comorbidities, myasthenic crisis, leukocytosis, elevated serum bilirubin and creatinine, and increased number of hospital admissions (P < 0.05). Myasthenia gravis is associated with comorbidities in majority of patients especially in late onset group, and more than two comorbidities are related to poor outcome.

Thymectomy in patients with myasthenia gravis increases the risk of autoimmune rheumatic diseases: a nationwide cohort study

Objectives

Previous studies have shown myasthenia gravis (MG) and autoimmune rheumatic diseases (ARDs) share common pathogenetic mechanisms. Therefore, the present study investigated the possible relationship between MG and ARDs.

Methods

We analysed Taiwanese medical data from the Registry of Catastrophic Illness and identified patients with MG. From the entire general population data of the National Health Insurance Research Database, we randomly selected a comparison cohort that was frequency-matched by age (in 5-year increments), sex, and index date. We analysed the risk of ARDs by using a Cox proportional hazards regression model stratified by sex, age and treatment.

Results

In the present study, we enrolled 6478 patients with MG (58.03% women; mean age, 50.55 years) and 25 912 age- and sex-matched controls. The risk of total ARDs was 6.25 times higher in the MG cohort than in the non-MG cohort after adjustment for age and sex. Furthermore, the MG cohort was associated with a significantly higher risk of primary SS (pSS), SLE and other ARD types (adjusted hazard ratios: 15.84 [95% CI: 8.39, 23.91]; 11.32 [95% CI: 5.04, 25.429]; and 4.07 [95% CI: 1.31, 12.62], respectively). The MG cohort who underwent thymectomy had an increased risk of RA, pSS and SLE (adjusted hazard ratios: 4.41; 15.06; and 23.68, respectively).

Conclusion

The present nationwide cohort study revealed an association between MG and incident ARDs. The MG cohort who underwent thymectomy had an increased risk of RA, pSS and SLE. Future studies are needed to elucidate the underlying pathogenesis and to translate this into clinical therapeutic options.