Increasing incidence of elderly onset patients with myasthenia gravis in a local area of Japan

Epidemiology of myasthenia gravis in France: Incidence, prevalence, and comorbidities based on national healthcare insurance claims data

BACKGROUND

The European literature has reported high variability in the incidence and prevalence rates of myasthenia gravis (MG), but no specific epidemiological data for France have been published. This study aimed to assess the incidence and prevalence rates of myasthenia gravis in France based on data extracted from the French National Health Insurance Claims Database (the SNIIRAM database).

METHODS

We conducted a retrospective repeated cross-sectional population study from 2008 to 2018 using a representative sample of the French population (Échantillon généraliste des bénéficiaires) covered by health insurance. We calculated the incidence, prevalence, and sex ratio of MG and screened for comorbidities associated with MG (standardized to the general population).

RESULTS

In total, 331 MG patients were identified between 2008 and 2018. The average incidence of MG in France was 50 per million person-years, while the mean prevalence was 465 per million people. The female-to-male ratio was 1.33. The Incidence of MG gradually increased from 40years of age for women and 60 for men. Thymoma was present for 5.1% of MG patients and a thymectomy was performed for 4.7%. Thyroid disease was the most prevalent autoimmune comorbidity, affecting approximately 8.5% of cases. MG patients had an increased cancer risk, with a standardized rate ratio of 2.38 (95% CI: 1.64-3.46).

CONCLUSION

The incidence and prevalence rates of MG are significantly higher than those previously reported in the literature and the incidence increases with age. The excess risk of cancer raises concerns for MG patients, in particular, concerning the management of immunosuppressive drugs.

Incidence and prevalence of myasthenia gravis in the United States: A claims-based analysis

INTRODUCTION/AIMS

Myasthenia gravis (MG) is a rare neuromuscular disorder with geographically variable prevalence and incidence rates. A global trend of increasing prevalence of MG has been observed in the last few decades, and this study aimed to assess the current prevalence and incidence rates of MG in the United States.

METHODS

Data were extracted from the Clarivate Real-World Data Repository (2016-2021), a US claims and electronic health records database. The prevalence and incidence of MG were calculated for the year 2021 for males and females who were <2, 2-5, 6-11, 12-17, 18-49, 50-64, and ≥65 years of age, using population estimates from the US Census.

RESULTS

The diagnosed prevalence and incidence of MG in the United States in 2021 were calculated to be 37.0 per 100,000 persons and 3.1 per 100,000 persons, respectively. While the incidence and prevalence of MG increased with age in both men and women, higher prevalence and incidence of MG were observed in younger women (<50 years) compared with men of matching age, and in older men (≥65 years) compared with women of the same age group.

DISCUSSION

The updated prevalence and incidence of MG in the United States in 2021 are higher than previous reports from the 1980s and early 2000s, following a global trend of increased prevalence and incidence for this disorder in the last few decades.

The Incidence of Myasthenia Gravis in the Province of Ferrara, Italy, in the Period of 2008-2022: An Update on a 40-Year Observation and the Influence of the COVID-19 Pandemic

Myasthenia gravis (MG) is the most common neuromuscular junction disorder. We evaluated the MG incidence rate in the province of Ferrara, Northern Italy, over two time frames (2008-2018 and 2019-2022, i.e., the COVID-19 pandemic) and considered early-onset (EOMG), late-onset (LOMG), and thymoma- and non-thymoma-associated MG. Moreover, in the second period, we assessed its possible relationship with SARS-CoV-2 infection or COVID-19 vaccination. We used a complete enumeration approach to estimate the MG incidence and its temporal trend. For the period of 2008-18, 106 new cases were identified (mean incidence rate 2.7/100,000 people). The highest rates were observed for the over-70 age group and in rural areas, with 17% of thymoma-associated MG. During the COVID-19 period, 29 new cases were identified (average incidence rate 2.1/100,000 people), showing a marked (though not statistically significant) decrease in the mean annual incidence compared to the previous period. Again, the highest rate was observed for the over-70 age group. The first period was in line with our previous observations for the period between 1985 and 2007, highlighting a rising incidence of LOMG and a marked decrease in EOMG. During the COVID-19 period, incidence rates were lower in the first years whereas, when the pandemic ended, the previous trend was confirmed.

Myasthenia Gravis: Novel Findings and Perspectives on Traditional to Regenerative Therapeutic Interventions

The prevalence of myasthenia gravis (MG), an autoimmune disorder, is increasing among all subsets of the population leading to an elevated economic and social burden. The pathogenesis of MG is characterized by the synthesis of autoantibodies against the acetylcholine receptor (AChR), low-density lipoprotein receptor-related protein 4 (LRP4), or muscle-specific kinase at the neuromuscular junction, thereby leading to muscular weakness and fatigue. Based on clinical and laboratory examinations, the research is focused on distinguishing MG from other autoimmune, genetic diseases of neuromuscular transmission. Technological advancements in machine learning, a subset of artificial intelligence (AI) have been assistive in accurate diagnosis and management. Besides, addressing the clinical needs of MG patients is critical to improving quality of life (QoL) and satisfaction. Lifestyle changes including physical exercise and traditional Chinese medicine/herbs have also been shown to exert an ameliorative impact on MG progression. To achieve enhanced therapeutic efficacy, cholinesterase inhibitors, immunosuppressive drugs, and steroids in addition to plasma exchange therapy are widely recommended. Under surgical intervention, thymectomy is the only feasible alternative to removing thymoma to overcome thymoma-associated MG. Although these conventional and current therapeutic approaches are effective, the associated adverse events and surgical complexity limit their wide application. Moreover, Restivo et al. also, to increase survival and QoL, further recent developments revealed that antibody, gene, and regenerative therapies (such as stem cells and exosomes) are currently being investigated as a safer and more efficacious alternative. Considering these above-mentioned points, we have comprehensively reviewed the recent advances in pathological etiologies of MG including COVID-19, and its therapeutic management.

The growing burden of generalized myasthenia gravis: a population-based retrospective cohort study in Taiwan

Background

The prevalence of myasthenia gravis is increasing in many countries, including Asia. As treatment options expand, population-based information about the disease burden can inform health technology assessments.

Methods

We conducted a population-based retrospective cohort study using the Taiwan National Healthcare Insurance Research database and Death Registry to describe the epidemiology, disease burden and treatment patterns of generalized myasthenia gravis (gMG) from 2009 to 2019. Episodes of hepatitis B virus (HBV) infection or reactivation were explored.

Results

The number of patients with gMG increased from 1,576 in 2009 to 2,638 in 2019 and the mean (standard deviation) age from 51.63 (17.32) to 55.38 (16.29) years. The female:male ratio was 1.3:1. Frequently reported co-morbidities were hypertension (32-34% of patients), diabetes mellitus (16-21%) and malignancies (12-17%). The prevalence of patients with gMG increased annually from 6.83/100,000 population in 2009 to 11.18/100,000 population in 2019 (p < 0.0001). There was no temporal trend in all-cause fatality rates (range 2.76-3.79/100 patients annually) or gMG incidence rates (2.4-3.17/100,000 population annually). First-line treatment was with pyridostigmine (82%), steroids (58%), and azathioprine (11%). There was minimal change in treatment patterns over time. Among 147 new HBV infections, 32 (22%) received ≥4 weeks of antiviral therapy suggesting chronic infection. The HBV reactivation rate was 7.2%.

Conclusion

The epidemiology of gMG in Taiwan is evolving rapidly, with higher prevalence rates and increasing involvement of older age-groups suggesting a growing burden of disease and associated healthcare costs. HBV infection or reactivation may pose a previously unrecognized recognized risk for patients with gMG receiving immunosuppressants.

Clinical Characteristics and Prognosis of Very late-onset Myasthenia Gravis in China

Alteration in onset-age distribution in myasthenia gravis (MG) and its increasing prevalence among the elderly underscores the need for a better understanding of the clinical course of MG and the establishment of personalized treatment. In this study we reviewed the demographics, clinical profile, and treatment of MG. Based on onset age, eligible patients were classified as early-onset MG (onset age ≥18 and <50 years), late-onset MG (onset age ≥50 and <65 years), and very late-onset MG (onset age ≥65 years). Overall, 1160 eligible patients were enrolled. Patients with late- and very late-onset MG showed a male predominance (P=0.02), ocular MG subtype (P=0.001), and seropositivity for acetylcholine receptors and titin antibodies (P<0.001). In very late-onset MG, a lower proportion of patients retained minimal manifestations status or better, a higher proportion of patients had MG-related deaths (P<0.001), and a shorter maintenance time of minimal manifestation status or better was seen at the last follow-up (P=0.007) than that in patients with early- and late-onset MG. Non-immunotherapy may associated with a poor prognosis in patients in the very late-onset group. Further studies on very late-onset MG patients should be performed to evaluate the relationship between immunotherapy and prognosis.

Surgical safety analysis and clinical experience sharing of myasthenia gravis patients aged 65 and over

BACKGROUND

To evaluate the surgical safety in myasthenia gravis (MG) patients aged 65 and over.

METHODS

A total of 564 patients with MG who underwent surgery in the Department of Thoracic Surgery of Beijing Hospital from November 2011 to March 2022 were included in the study and divided into two groups taking the age of 65 as the boundary. Perioperative data of patients were recorded and statistically analyzed.

RESULTS

Compared with young patients, FEV1, FEV1% and MVV in lung function of elderly MG patients were worse (p < 0.001, p < 0.001, p = 0.002). Postoperative drainage time was longer (p < 0.001), combined with more drainage volume (p = 0.002). The American Society of Anesthesiologists (ASA) score of elderly MG patients was higher (p < 0.001). Complications were more likely to occur (p = 0.008) after surgery and Clavien-Dindo classification (CDC) of postoperative complications was also higher (p = 0.003). Meanwhile, postoperative myasthenic crisis (POMC) was more likely to occur (p = 0.038). Logistic regression showed that lower DLCO% (p = 0.049) was an independent risk factor for postoperative complications.

CONCLUSIONS

Surgical indications should be considered in each elderly MG patient on an individual basis. Moreover, most elderly MG patients safely survive the perioperative period and benefit from surgery through individualized consideration.

Immunotherapy for ocular myasthenia gravis: an observational study in Japan

Background

Treatment for ocular myasthenia gravis (OMG) has not yet been well established. Few reports have been published on the clinical practice and outcomes of OMG.

Objectives

We investigated treatment of OMG and its outcomes in Japan.We investigated treatment of OMG and its outcomes in Japan.

Design

We performed a retrospective cross-sectional survey of OMG patients from eight hospitals in Japan.

Methods

Clinical information, including sex, age at onset, initial symptoms, autoantibodies, clinical course, treatment history, complications, and outcomes, was obtained. In addition, we recorded the total number of patients with MG and OMG separately.

Results

In total, 135 patients with OMG (67 men, 68 women) were included. Treatment of OMG was not simple and involved various immunotherapeutic strategies. Eight patients went into remission spontaneously without immunotherapy. A total of 117 patients showed improvements after treatment, whereas 10 patients showed refractory responses to treatment. Overall outcomes were good; however, symptoms persisted in 60.7% of patients even after treatment. Among 90 patients who received immunotherapy, only two showed a refractory response. Meanwhile, for 45 patients who did not receive immunotherapy, 8 were refractory. Thus, the rate of refractory disease in the group with immunotherapy was significantly lower (p = 0.001, u-test) than in the group without immunotherapy. The proportion of generalized MG patients among all MG cases was low in medical centers where immunotherapy for OMG was frequently performed.

Conclusion

Although the overall prognosis for patients with OMG was good, symptoms remained in more than half of the patients. Immunotherapy, including corticosteroids, may be beneficial for patients with OMG.

Plain language summary

Is immunosuppressive therapy beneficial for myasthenia gravis patients with ocular symptoms only? Patients with ocular myasthenia gravis (OMG) have only eye symptoms for more than 2 years. Whether this condition is an initial stage of the disease before eventually progressing to generalized myasthenia gravis (gMG) is still uncertain. Different from gMG, OMG is not life-threatening. But eye symptoms often cause troublesome problems in life. Doctors have treated OMG patients similarly to patients with gMG. There is no standard clinical practice for OMG. In this study, we examined how patients with OMG were treated at eight different specialist centers in Japan. In 135 patients with OMG, 8 patients became symptom free without treatment, 117 patients showed improvements after treatment, whereas 10 patients did not get well. Overall outcomes were good, but symptoms remained in 60.7% of patients even after treatment. Among 90 patients who received one or more immunotherapies, only 2 did not get well. Meanwhile, for 45 patients who did not receive immunotherapy, 8 remained ill. We found that treatment of OMG was not simple and often needed multiple immunotherapies. Administering immunotherapy, including corticosteroids, may be beneficial for patients with OMG.

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.

[Clinical and paraclinical profile of autoimmune myasthenia gravis in Ouagadougou, Burkina Faso]

INTRODUCTION

Certain differences in the epidemiological, clinical, paraclinical and evolution profiles of autoimmune myasthenia gravis (AIMG) are increasingly described in patients according to geographic origins. The present study was carried out in order to help characterize the socio-demographic, clinical and paraclinical profile of AIMG in Ouagadougou, Burkina Faso.

PATIENTS AND METHODS

This was a cross-sectional, descriptive, multicenter, hospital study carried out in Ouagadougou (Burkina Faso), over a period of 5 years 6 months, from March 2015 to September 2019. The study concerned all patients who had a clinical symptomatology suggestive of myasthenia gravis, associated with the presence in the serum of anti-AChR Ab and / or anti-MuSK Ab and / or the presence of a >10% decrement in electroneuromyography and / or a positive therapeutic test for oral anticholinestherasics. Sociodemographic, clinical and paraclinical variables, were analyzed.

RESULTS

A total of 25 patients (15 women and 10 men), were included. The young adult form was predominant (20 cases). The median time between the first symptoms and the diagnosis was 28.4 months +/- 44.8 (2 - 217 months). Diplopia and/or ptosis (80%) and dysphonia (72%) were the most frequent revealing clinical presentations. On admission, 7 patients (28%) had a moderate generalized form (MGFA class III) and 9 patients (36%) had a severe to very severe generalized form (MGFA class IV to V). Plasma Ab assays were performed in 17 patients (68%): anti-RACh Ab were positive in 11 patients (64.7%) and anti-MuSK Ab in 3 patients (14.3%). Thoracic CT revealed thymus hyperplasia in 12 patients (48%), thymoma in 5 patients (20%). Hyperthyroidism was associated in 2 patients (8%).

CONCLUSION

AIMG in Ouagadougou, Burkina Faso is marked by delayed diagnosis, a predominance in young women, severe generalized forms and a high frequency of plasma anti-MuSK Ab. This profile appears to be different from that of Caucasian patients. Collaborative studies in the sub-Saharan region on AIMG in general populations are needed.

Very late onset neuromyelitis optica spectrum disorders

BACKGROUND AND PURPOSE

Neuromyelitis optica spectrum disorder (NMOSD) often presents in the elderly with an insidious onset of symptoms and aggressive progression. There have been anecdotal cases of very late onset (VLO)-NMOSD, but case series reports are rare. The aim of this retrospective study was to clarify the clinical features of VLO-NMOSD.

METHODS

According to the age at onset, we classified patients with NMOSD into three subgroups: ≤49 years, early onset NMOSD (EO-NMOSD); 50-69 years, late onset NMOSD (LO-NMOSD); and ≥70 years, VLO-NMOSD. We evaluated the clinical characteristics, magnetic resonance imaging (MRI) findings, laboratory data, and immunotherapies of the groups.

RESULTS

Overall, 12 men and 64 women with a median (interquartile range) age at onset and duration of disease of 42.0 (29.0-55.8) years and 70.0 (16.3-143.0) months, respectively, were included. Eight (11%) patients had VLO-NMOSD, 22 (29%) had LO-NMOSD, and 46 (61%) had EO-NMOSD. Patients with EO-NMOSD had a significantly longer interval between episodes as well as time between the first symptom and diagnosis of NMOSD than did those with VLO-NMOSD and LO-NMOSD (p = 0.046). Optic neuritis and nerve lesions on MRI were significantly less frequent in patients with VLO-NMOSD than in those with LO-NMOSD and EO-NMOSD (p = 0.002 and p = 0.028, respectively). In contrast, patients with VLO-NMOSD had higher nadir Expanded Disability Status Scale and Nurick scale scores and a significantly longer spinal lesion length than did those with LO-NMOSD and EO-NMOSD (p = 0.029, p = 0.049, and p = 0.032, respectively).

CONCLUSIONS

Patients with VLO-NMOSD tend to develop severe myelitis with long cord lesions but not optic neuritis.

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.

Myasthenia Gravis in Poland: National Healthcare Database Epidemiological Study

INTRODUCTION

Myasthenia gravis (MG) is a rare autoimmune disorder of the neuromuscular junction. MG epidemiology has not been studied in Poland in a nationwide study before.

METHODS

Our epidemiological data were drawn from the National Health Fund (Narodowy Fundusz Zdrowia, NFZ) database; an MG patient was defined as a person who received at least once medical service coded in ICD-10 as MG (G70) and at least 2 reimbursed prescriptions for pyridostigmine bromide (Mestinon®) or ambenonium chloride (Mytelase®) in 2 consecutive years.

RESULTS

On 1st of January 2019, 8,702 patients with MG were receiving symptomatic treatment (female:male ratio: 1.65:1). MG incidence was 2.36/100,000. The mean age of incident cases in 2018 was 61.37 years, 59.17 years for women and 64.12 years for men. Incidence of early-onset MG (<50 years) was 0.80/100,000 and 4.98/100,000 for late-onset MG (LOMG), with male predominance in LOMG. Prevalence was 22.65/100,000. In women, there was a constant increase in prevalence of symptomatic MG from the first decade of life up to 80-89 years. In men, an increase in prevalence appeared in the 6th decade. The highest prevalence was observed in the age group of 80-89 years: 59.65/100,000 in women and 96.25/100,000 in men.

CONCLUSIONS

Our findings provide information on epidemiology of MG in Poland and can serve as a tool to evaluate healthcare resources needed for MG patients.

Human Leukocyte Antigen Class II associations in late-onset Myasthenia Gravis

Objective

Genetic factors predisposing to late‐onset myasthenia gravis (LOMG) have not been clearly defined yet. However, genome‐wide association studies identified Human Leukocyte Antigen (HLA) Class II alleles as a hotspot in this disease subtype. The aim of this study was to analyze the correlations of HLA Class II alleles with clinical data and titin antibodies in this patient subgroup.

Methods

This study consecutively enrolled anti‐acetylcholine receptor antibody‐positive, non‐thymoma patients with generalized LOMG. All patients were of Italian ancestry. HLA‐DRB1 and ‐DQB1 genotyping and serum titin antibody testing were performed in this population.

Results

A total of 107 patients (females: 28/107, 26.2%; median age of onset: 68 years, range: 50‐92) were included. We found a positive association with HLA‐DRB1*07 (P = 1.1 × 10^‐5), HLA‐DRB1*14 (P = 0.0251) and HLA‐DQB1*02 (P = 0.0095). HLA‐DRB1*03, HLA‐DRB1*11, and HLA‐DQB1*03 were protective alleles (P = 7.9 × 10^‐5, P = 0.0104, and P = 0.0067, respectively). By conditional haplotype analysis, HLA‐DRB1*07‐DQB1*02 was found to be the major risk haplotype (OR = 4.10; 95% C.I.: 2.80‐5.99; P = 6.01 × 10^‐11). The mean age at onset was 73.4 years in DRB1*07 homozygotes, 69.7 years in heterozygotes, and 66.6 in non‐carriers (P = 0.0488). DRB1*07 carriers and non‐carriers did not differ in disease severity and response to therapy. Titin antibodies were detected in 61.4% of the cases, having no association with HLA alleles or specific clinical characteristics.

Interpretation

In our study, we identified the HLA DRB1*07‐DQB1*02 haplotype as a predisposing factor for the development of generalized LOMG in the Italian population.

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.

Incidence, mortality, and economic burden of myasthenia gravis in China: A nationwide population-based study

Background

Myasthenia gravis (MG) is the most common primary disorder of neuromuscular transmission, but the incidence of MG in China is unknown. We conducted the first nationwide study to determine the incidence and mortality rates of MG in all age groups at the national level in China.

Methods

This national population-based registry study is based on the database of the Hospital Quality Monitoring System of National Health Commission, which covers 1665 hospitals providing myasthenia gravis care in 31 provinces and municipalities across China. 94,638 hospital admissions for 59,243 myasthenia gravis patients were identified from January 1st, 2016 to December 31st, 2018. Myasthenia gravis was identified by ICD-10 codes (G70). Incidence of myasthenia gravis was stratified by age, sex, and province.

Findings

Of 59,243 patients, 30,503 individuals with myasthenia gravis were newly diagnosed. Age and sex adjusted incidence of myasthenia gravis was 0.68 per 100,000 person-years, with highest in the age group of 70–74 years. The incidence in females was 0.76 per 100,000 and 0.60 per 100,000 in males. The admission mortality rate was 14.69‰. Respiratory failure was the leading cause of death in patients with myasthenic crisis. There were 14,840 patients with thymomas, encompassing 14,636 (26.5%) adults and 204 (7.1%) juveniles. 9453 (63.7%) patients with thymomas underwent thymomectomy. The median length of hospital stay was 8 days (interquartile range (IQR) 4 to 15 days) with median hospitalization cost $1037 (IQR $493 to $2925). The Basic Medical Insurance was the most common payment method, covering 67.4% of patients.

Interpretation

The age and sex adjusted incidence of MG was 0.68 per 100,000 person-years in China. The admission mortality rate was 14.69‰. Most cases of new onset MG occurred in the seventh decade of life.

Funding

National Science Foundation of China (91642205, and 81830038); Advanced Innovation Center for Human Brain Protection, Capital Medical University, Beijing

Incidence of AChR Ab-positive myasthenia gravis in Israel: A population-based study

BACKGROUND

The incidence of myasthenia gravis (MG) has traditionally been low, ranging between 2-6/10⁶ . Several recent epidemiological studies have reported a higher incidence. We, therefore, aimed to assess and characterize the incidence of MG in Israel.

METHODS

We retrospectively reviewed the records of all four laboratories that performed the acetylcholine receptor antibody (AChR Ab) test in Israel between 1994 and 2013 and documented the number of newly diagnosed seropositive MG patients each year. To assure that data indeed reflect only newly diagnosed patients, patient's names and ID numbers were screened at the Hadassah medical center database since 1978, the year when the test was first performed in Israel. In order to calculate the annual incidence of the disease, the population at risk was derived from the annual publication of the Israeli Central Bureau of Statistics.

RESULTS

The annual incidence of MG for this time period was 13.1/10⁶ inhabitants. The mean incidence of MG between 1994 and 2003 was 7.695/10⁶ /y, while the mean incidence between 2004 and 2013 was 18.49/10⁶ (P < .0001). Mean age of diagnosis between 1994 and 2003 was 56.65 ± 0.9351, while between 2004 and 2013, it was 59.89 ± 0.5336 (P = .0012). Male to female (M:F) incidence ratio in the years 1994-2003 and 2004-2013 was 2:3.2 and 3:1.8, respectively, reflecting increased incidence among males (P < .0001).

CONCLUSIONS

The incidence of MG in Israel has increased significantly during the last decade, especially among males of older age. These findings may reflect an etiological role of an environmental factor, increased awareness, and increased longevity in general.

Clinical and therapeutic features of myasthenia gravis in adults based on age at onset

OBJECTIVE

To describe the characteristics of patients with very-late-onset myasthenia gravis (MG).

METHODS

This observational cross-sectional multicenter study was based on information in the neurologist-driven Spanish Registry of Neuromuscular Diseases (NMD-ES). All patients were >18 years of age at onset of MG and onset occurred between 2000 and 2016 in all cases. Patients were classified into 3 age subgroups: early-onset MG (age at onset <50 years), late-onset MG (onset ≥50 and <65 years), and very-late-onset MG (onset ≥65 years). Demographic, immunologic, clinical, and therapeutic data were reviewed.

RESULTS

A total of 939 patients from 15 hospitals were included: 288 (30.7%) had early-onset MG, 227 (24.2%) late-onset MG, and 424 (45.2%) very-late-onset MG. The mean follow-up was 9.1 years (SD 4.3). Patients with late onset and very late onset were more frequently men (p < 0.0001). Compared to the early-onset and late-onset groups, in the very-late-onset group, the presence of anti-acetylcholine receptor (anti-AChR) antibodies (p < 0.0001) was higher and fewer patients had thymoma (p < 0.0001). Late-onset MG and very-late-onset MG groups more frequently had ocular MG, both at onset (<0.0001) and at maximal worsening (p = 0.001). Although the very-late-onset group presented more life-threatening events (Myasthenia Gravis Foundation of America IVB and V) at onset (p = 0.002), they required fewer drugs (p < 0.0001) and were less frequently drug-refractory (p < 0.0001).

CONCLUSIONS

Patients with MG are primarily ≥65 years of age with anti-AChR antibodies and no thymoma. Although patients with very-late-onset MG may present life-threatening events at onset, they achieve a good outcome with fewer immunosuppressants when diagnosed and treated properly.

Hospital and healthcare insurance system record-based epidemiological study of myasthenia gravis in southern and northern China

OBJECTIVE

This is the first cross-region epidemiological study of myasthenia gravis (MG) in China. We estimated the incidence, prevalence, and medical costs of MG in southern China and explored the differences between the southern and northern Chinese populations.

METHODS

We collected and analyzed records from 20 hospitals in the southern city, Guangzhou, 13 hospitals in the northern city, Harbin, and two healthcare insurance systems: job based and residence based in Guangzhou during 2000-2017.

RESULTS

(1) The estimated annual incidence of MG was 1.55-3.66 per 100,000, and the estimated prevalence of MG was 2.19-11.07 per 100,000 in southern China based on insurance records. (2) The proportion of hospitalized MG patients in the south-based hospital records was three times as high as that in the north-based hospital records. (3) Female MG prevalence was significantly higher than male MG prevalence in Guangzhou, while the similar gender difference in Harbin was not statistically significant due to higher variation in earlier years. (4) The average expense was $35-42 for each outpatient service and $2526-2673 for each hospitalization expense in the south. (5) Contrary to the increase of insurance-based estimate of MG prevalence, the proportion of hospitalized MG patients did not increase over the years, suggesting rising awareness and utilization of health insurance.

CONCLUSIONS

The southern MG population had a significantly higher prevalence and a lower response threshold to medication than the northern MG population. These results are calling for further investigations on the genetic, cultural, and environmental variations of the Chinese MG populations between north and south.

Neuromuscular junction disorders

Diseases of the neuromuscular junction comprise a wide range of disorders. Antibodies, genetic mutations, specific drugs or toxins interfere with the number or function of one of the essential proteins that control signaling between the presynaptic nerve ending and the postsynaptic muscle membrane. Acquired autoimmune disorders of the neuromuscular junction are the most common and are described here. In myasthenia gravis, antibodies to acetylcholine receptors or to proteins involved in receptor clustering, particularly muscle-specific kinase, cause direct loss of acetylcholine receptors or interfere with the agrin-induced acetylcholine receptor clustering necessary for efficient neurotransmission. In the Lambert-Eaton myasthenic syndrome (LEMS), loss of the presynaptic voltage-gated calcium channels results in reduced release of the acetylcholine transmitter. The conditions are generally recognizable clinically and the diagnosis confirmed by serologic testing and electromyography. Screening for thymomas in myasthenia or small cell cancer in LEMS is important. Fortunately, a wide range of symptomatic treatments, immunosuppressive drugs, or other immunomodulating therapies is available. Future research is directed to understanding the pathogenesis, discovering new antigens, and trying to develop disease-specific treatments.

Incidence and Prevalence of Myasthenia Gravis in Korea: A Population-Based Study Using the National Health Insurance Claims Database

Background and Purpose

There have been a few national population-based epidemiological studies of myasthenia gravis (MG) with wide variation of incidence and prevalence rates worldwide. Herein we report the first nationwide population-based epidemiological study of MG in Korea.

Methods

We attempted to estimate the incidence and prevalence rates of MG using the Korean National Health Insurance claims database for 2010 to 2013. Cases with MG were defined as those having claim records with a principal diagnosis of MG and the prescription of acetylcholinesterase inhibitors or immunosuppressive agents including corticosteroids and azathioprine within 2 years after the diagnosis. The year 2010 was set as a washout period, such that patients were defined as incident cases if their first records of MG were observed in 2011.

Results

In 2011 there were 1,236 incident cases, and the standardized incidence rate was 2.44 per 100,000 person-years. The standardized prevalence rates were 9.67 and 10.66 per 100,000 persons in 2010 and 2011, respectively. The incidence and prevalence rates peaked in the elderly population aged 60 to 69 years for both sexes.

Conclusions

This is one of the largest national population-based epidemiological studies of MG, and it has confirmed the high incidence and prevalence rates of MG in the elderly population of South Korea.

Late-onset myasthenia gravis is predisposed to become generalized in the elderly

Objective

The continuous increase in the number of patients presenting with late-onset myasthenia gravis (LOMG) underscores the need for a better understanding of the clinical course and the establishment of an optimal therapeutic strategy. We aimed to clarify factors associated with clinical outcomes in LOMG.

Methods

We retrospectively reviewed the clinical profiles of 40 patients with early-onset MG (EOMG) (onset age: 49 years or younger), 30 patients with non-elderly LOMG (onset age: 50–64 years), and 28 patients with elderly LOMG (onset age: 65 years or older) and compared the subgroups according to onset age and thymus status. The evaluated parameters were MGFA classification before treatment, MG-ADL score, complicating diseases, antibody titer, treatment, and MGFA post-intervention status.

Results

Elderly LOMG patients showed transition to generalized symptoms at a higher frequency and underwent thymectomy less frequently than EOMG and non-elderly LOMG patients (p < 0.001). The frequencies of crisis and plasmapheresis were significantly lower in thymectomized LOMG patients without thymoma than in thymectomized LOMG patients with thymoma or non-thymectomized LOMG patients (p < 0.01, P < 0.05, respectively). However, the outcome was not significantly different. All of the thymectomized LOMG patients without thymoma presenting with hyperplasia or thymic cyst had a favorable clinical course.

Conclusions

Our study showed that elderly LOMG patients are more prone to severity, suggesting that they require aggressive immunomodulatory therapy.

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Elderly LOMG patients showed transition to generalized symptoms at a higher frequency.

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Thymectomized LOMG patients without thymoma showed crisis less frequently.

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Our study showed that elderly LOMG patients are more prone to severity.

Myasthenia gravis: a clinical-immunological update

Myasthenia gravis (MG) is the archetypic disorder of both the neuromuscular junction and autoantibody-mediated disease. In most patients, IgG1-dominant antibodies to acetylcholine receptors cause fatigable weakness of skeletal muscles. In the rest, a variable proportion possesses antibodies to muscle-specific tyrosine kinase while the remainder of seronegative MG is being explained through cell-based assays using a receptor-clustering technique and, to a lesser extent, proposed new antigenic targets. The incidence and prevalence of MG are increasing, particularly in the elderly. New treatments are being developed, and results from the randomised controlled trial of thymectomy in non-thymomatous MG, due for release in early 2016, will be of particular clinical value. To help navigate an evidence base of varying quality, practising clinicians may consult new MG guidelines in the fields of pregnancy, ocular and generalised MG (GMG). This review focuses on updates in epidemiology, immunology, therapeutic and clinical aspects of GMG in adults.

Relationship between Urinary N-Desmethyl-Acetamiprid and Typical Symptoms including Neurological Findings: A Prevalence Case-Control Study

Neonicotinoid insecticides are nicotinic acetylcholine receptor agonists used worldwide. Their environmental health effects including neurotoxicity are of concern. We previously determined a metabolite of acetamiprid, N-desmethyl-acetamiprid in the urine of a patient, who exhibited some typical symptoms including neurological findings. We sought to investigate the association between urinary N-desmethyl-acetamiprid and the symptoms by a prevalence case-control study. Spot urine samples were collected from 35 symptomatic patients of unknown origin and 50 non-symptomatic volunteers (non-symptomatic group, NSG, 4–87 year-old). Patients with recent memory loss, finger tremor, and more than five of six symptoms (headache, general fatigue, palpitation/chest pain, abdominal pain, muscle pain/weakness/spasm, and cough) were in the typical symptomatic group (TSG, n = 19, 5–69 year-old); the rest were in the atypical symptomatic group (ASG, n = 16, 5–78 year-old). N-desmethyl-acetamiprid and six neonicotinoids in the urine were quantified by liquid chromatography-tandem mass spectrometry. The detection of N-desmethyl-acetamiprid was the most frequent and highest in TSG (47.4%, 6.0 ppb (frequency, maximum)), followed by in ASG (12.5%, 4.4 ppb) and in NSG (6.0%, 2.2 ppb), however acetamiprid was not detected. Thiamethoxam was detected in TSG (31.6%, 1.4 ppb), in ASG (6.3%, 1.9 ppb), but not in NSG. Nitenpyram was detected in TSG (10.5%, 1.2 ppb), in ASG (6.3%, not quantified) and in NSG (2.0%, not quantified). Clothianidin was only detected in ASG (6.3%, not quantified), and in NSG (2.0%, 1.6 ppb). Thiacloprid was detected in ASG (6.3%, 0.1 ppb). The cases in TSG with detection of N-desmethyl-acetamiprid and thiamethoxam were aged 5 to 62 years and 13 to 62 years, respectively. Detection of N-desmethyl-acetamiprid was associated with increased prevalence of the symptoms (odds ratio: 14, 95% confidence interval: 3.5–57). Urinary N-desmethyl-acetamiprid can be used as a biomarker for environmental exposure to acetamiprid. Further multi-centered clinical research in larger patients groups with more metabolites analysis is needed.

Complicating autoimmune diseases in myasthenia gravis: a review

Myasthenia gravis (MG) is a rare autoimmune disease of skeletal muscle endplates. MG subgroup is relevant for comorbidity, but usually not accounted for. MG patients have an increased risk for complicating autoimmune diseases, most commonly autoimmune thyroid disease, systemic lupus erythematosus and rheumatoid arthritis. In this review, we present concomitant autoimmune disorders associated with the different MG subgroups, and show how this influences treatment and prognosis. Concomitant MG should always be considered in patients with an autoimmune disorder and developing new neuromuscular weakness, fatigue or respiratory failure. When a second autoimmune disorder is suspected, MG should be included as a differential diagnosis.

Prognostic factors and health-related quality of life in ocular Myasthenia Gravis (OMG)

We evaluate the factors predictive of prognosis in 91 Caucasian patients affected by ocular myasthenia gravis (OMG), followed at our Institution during an observational time, ranging from 12 to 240 months. The Myasthenia Gravis Foundation of America (MGFA) clinical classification was used to grade the disease severity. We considered as outcome measures the variation in two subscores, ocular (O-QMG) and nonocular (NO-QMG); the last one reflected bulbar, neck, extremity functions. None of the independent variables evaluated for association with the outcome, as age of onset, type of therapy, length of interval between first and last examinations, and presence of antibodies to acetylcholine receptors (AChR-Abs) significantly affected the evolution of O-QMG and of NO-QMG. Health-related quality of life (HRQol) was assessed in 63 patients. Variations of diplopia or ptosis did not affect significantly physical (PCS) or mental composite subscores (MCS) of the Short-Form Health Survey (SF-36). Human leukocyte antigen (HLA) genotyping was studied to explore whether HLA class I and II allelic distribution differed among MG patients and controls. None of the studied HLA alleles significantly differed between OMG patients and controls. Similarly, none of the alleles with frequencies higher than 15% either in OMG patients or in controls was significantly associated, after Bonferroni correction, with the presence or absence of anti-AChR-Abs in serum.

Epidemiological study of adult-onset myasthenia gravis in the area of Belgrade (Serbia) in the period 1979-2008

BACKGROUND

The aim of this study was to analyze the prevalence and incidence of adult-onset myasthenia gravis (MG) in the Belgrade population from 1979 to 2008.

METHODS

Data on the number of MG patients and their basic demographic and clinical characteristics were collected from hospital records (1979-1992) and the Belgrade MG Registry (1993-2008). Incidence and prevalence were standardized by the direct method (using the world standard population). A time-trend analysis of MG incidence was performed using a linear regression model.

RESULTS

During the study period 562 cases (316 women, 246 men) were registered. On December 31st, 2008, the standardized prevalence (according to the world standard population) was 188.3/1,000,000 (women: 237.8/1,000,000; men: 139.4/1,000,000). The average annual standardized incidence rate was 13.3/1,000,000 (women: 14.1/1,000,000; men: 12.2/1,000,000). The incidence rates tended to increase significantly in both sexes during the study period (y = 3.299 + 14.363x, p = 0.002). Age-specific incidence rates for women demonstrated a bimodal pattern, with the first peak in the 20- to 29-year age group and the second one in the ≥70-year group. For both genders, an increase in age-specific incidence rates was registered for all age groups, although this was significant (p = 0.001) only for an MG onset of ≥60 years of age.

CONCLUSIONS

The study confirms an increase in the incidence of MG in the area of Belgrade during the study period, especially for those with MG onset after 60 years of age.

Incidence of thymoma in myasthenia gravis: a systematic review

Background and Purpose

Myasthenia gravis (MG) is usually comorbid with thymoma. More accurate estimates of the incidence thymoma in MG will help inform patients and their physicians, facilitate health policy discussions, provide etiologic clues, and optimize the management of MG.

Methods

We conducted a systematic review search of relevant English-language studies published between 1960 and 2012 using MEDLINE and Embase. We identified additional studies by reviewing the bibliographies of the retrieved articles and hand searched the main neurology journals. Only incidence studies and case series of unselected MG patients in which information about thymoma were included.

Results

Out of 2206 potentially relevant studies, 49 met the inclusion criteria. Although there was a considerable degree of heterogeneity, the pooled estimate of the incidence of thymoma in MG was 21% (95% confidence interval, 20-22%). The pooled incidence was significantly higher for surgery-based studies than for population- and hospital-based studies. A large proportion of the reported thymomas were noninvasive. Furthermore, thymoma appears to occur significantly more frequently among male MG patients and those older than 40 years at the onset of MG.

Conclusions

Thymoma is common in MG patients, but appears to be found more often in male MG patients and those older than 40 years at the onset of MG. Further research is needed to expand our understanding of these association conditions.

Frequency of autoimmune diseases in myasthenia gravis: a systematic review

The course of myasthenia gravis (MG) may get complicated by the development of other autoimmune diseases. Estimates of the frequency of autoimmune diseases will help inform patients and physicians, direct health policy discussion, provide etiologic clues, and optimize the management of MG. However, the frequency of autoimmune diseases in people with MG is still uncertain. A systematic search for English language studies was conducted by MEDLINE and EMBASE from 1960 through 2010. Incidence studies and case series of all MG subtypes with information about autoimmune diseases were included; 25 studies met the inclusion criteria. Although there was considerable heterogeneity, the pooled estimate of the coexisting autoimmune diseases in MG was 13% (95% confidence interval, 12%-14%). Autoimmune thyroid disease seems to occur more frequently than other autoimmune conditions in MG patients. Heterogeneity in study estimates could be explained by ascertainment bias and case mix. Furthermore, autoimmune diseases occurred significantly more often in females and anti-acetylcholine receptor seropositive MG patients. Patients with MG have an increased frequency of coexisting autoimmune diseases. Autoimmune diseases seem to occur more often in female and seropositive MG patients. Further research is needed to expand our understanding of these associations.

Myasthenia gravis: a changing pattern of incidence

The annual incidence of myasthenia gravis (MG) ranges from 3 to 30 per 1,000,000 people. Since the mid-1980s, an increasing incidence has been reported, mainly due to late-onset MG. Whether the increase was due to population aging, improved diagnosis and case collection, or a true excess of incidence cases is still under debate. We used a complete enumeration approach by reviewing all possible sources of case collection in the province of Ferrara, Italy, to estimate the MG incidence and its temporal trend over the study period (1985-2007). The mean annual age-adjusted incidence of MG was 18 per 1,000,000, without any significant temporal trend. The incidence rates in the period 1985-1990 were 14 both for early and late-onset MG. Thereafter, a significant increase in incidence of late-onset MG (p < 0.05), and a decrease in early onset MG were detected (p < 0.01). These findings were related to nonthymoma MG. The median age at onset of the disease steadily increased over time. A changing pattern of MG incidence with an increase in frequency of late-onset and a decrease of early onset MG was found in the last years, giving a significant shift to older age at onset of the disease. Unknown environmental factors may have driven this change in MG epidemiology.