Myasthenia gravis: a higher than expected incidence in the elderly

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.

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.

Diagnosis and Management of Myasthenia Gravis

PURPOSE OF REVIEW

This article reviews updated diagnostic procedures and currently available treatment modalities for myasthenia gravis (MG).

RECENT FINDINGS

Patients with MG can be classified based on antibody status and their clinical presentation; treatment responses may differ based on disease subtypes. Improved diagnostic methods and recognition of new antigenic targets such as lipoprotein-related protein 4 have led to improved diagnostic efficiencies. Corticosteroids remain the first-line immunotherapy, but there is a trend toward minimizing their use at high doses and for long durations. Oral immunosuppressants such as mycophenolate mofetil, azathioprine, and tacrolimus remain useful. An international, multicenter randomized trial comparing thymectomy plus prednisone with prednisone alone demonstrated that thymectomy improves clinical outcomes in selected patients with nonthymomatous MG. Eculizumab, efgartigimod, and ravulizumab have recently been approved by the US Food and Drug Administration (FDA) for adult patients with generalized MG who are acetylcholine receptor-antibody positive. These drugs take advantage of novel mechanisms of action and expand treatment options for patients with MG. Data on rituximab suggest that it can be a good option, especially for patients with MG who are positive for antibodies against muscle-specific tyrosine kinase (MuSK). The number of clinical trials and drugs in development for MG is steadily increasing.

SUMMARY

The diagnosis of MG can generally be made from the patient's history, a neurologic examination, and laboratory and electrodiagnostic testing. Carefully selected treatment improves outcomes in MG. Additional treatment options for MG will likely be available in the near future.

Validation of myasthenia gravis diagnosis in the older Medicare population

INTRODUCTION/AIMS

Administrative health data has been increasingly used to study the epidemiology of myasthenia gravis (MG) but a case ascertainment algorithm is lacking. We aimed to develop a valid algorithm for identifying MG patients in the older population with Medicare coverage.

METHODS

Local older patients (age ≥65) who received healthcare at the Cleveland Clinic and possessed Medicare coverage in 2014 and 2015 were selected. Potential MG patients were identified by using a combination of ICD9 or ICD10 codes for MG and MG-related text-word search. Diagnosis was categorized as "definite MG", "possible MG" or "non-MG" after review of clinical summaries by 5 neuromuscular specialists. Performances of various algorithms were tested by use of the definite MG cohort as a reference standard, and calculation of sensitivity, specificity, and predictive values.

RESULTS

A total of 118 988 local older patients with Medicare coverage were identified. Usage of MG ICD codes and text-word search resulted in 125 patients with definite and 67 with possible MG. A total of 45 algorithms involving ICD usage, medication prescription, and specialty visit were tested. The best performing algorithm was identified as 2 office visits using MG ICD codes separated by at least 4 weeks or 1 hospital discharge and 1 office visit each using MG ICD codes separated by at least 4 weeks within the two-year period, resulting in a sensitivity and positive predictive value of 80% for identifying definite MG patients.

DISCUSSION

Algorithms using ICD codes can reliably identify patients with MG with a high degree of accuracy.

Lack of Immunotherapy as the Only Predictor of Secondary Generalization in Very-Late-Onset Myasthenia Gravis With Pure Ocular Onset

During the past two decades, an increasing number of patients with very-late-onset myasthenia gravis (v-LOMG) with an onset age of 65 years or older have been identified. However, few studies explore the predictors of secondary generalization in patients with v-LOMG with pure ocular onset. In this retrospective cohort study, 69 patients with v-LOMG were divided into ocular MG (OMG) and generalized MG (GMG), and the clinical characteristics and outcomes were compared. Cox regression analysis was performed to explore the predictors of generalization. The average onset age of the study population was 73.1 ± 4.2 years and the median disease duration was 48.0 months (interquartile range, 32.5-64.5 months). Serum acetylcholine receptor (AChR) antibody was detected in up to 86% of patients and concomitant diseases in approximately half of the patients. Male predominance was seen in OMG group while female predominance in GMG group (p = 0.043). Patients with OMG showed a lower positive rate of repetitive nerve stimulation (RNS) than those with GMG (p = 0.014), and favorable outcomes were obtained in more patients with OMG than those with GMG (p < 0.001). Of the 51 patients with pure ocular onset, 25 (49.0%) underwent secondary generalization. A higher probability of generalization was found in patients with positive RNS results and without immunotherapy (p = 0.018 and <0.001). Upon Cox regression analysis, immunotherapy was negatively associated with secondary generalization [HR (hazard ratio) 0.077, 95%CI [0.024-0.247], p < 0.001]. Altogether, compared to the patients with very-late-onset GMG, the counterparts with OMG exhibit a significantly higher female predominance and a lower positive rate of RNS tests, especially on facial and accessory nerves. Lack of immunotherapy is the only predictor of secondary generalization in those with pure ocular onset.

Characteristics, treatment, and outcomes of Myasthenia Gravis in COVID-19 patients: A systematic review

Objective

Recent studies suggest that the clinical course and outcomes of patients with coronavirus disease 2019 (COVID-19) and myasthenia gravis (MG) are highly variable. We performed a systematic review of the relevant literature with a key aim to assess the outcomes of invasive ventilation, mortality, and hospital length of stay (HLoS) for patients presenting with MG and COVID-19.

Methods

We searched the PubMed, Scopus, Web of Science, and MedRxiv databases for original articles that reported patients with MG and COVID-19. We included all clinical studies that reported MG in patients with confirmed COVID-19 cases via RT-PCR tests. We collected data on patient background characteristics, symptoms, time between MG and COVID-19 diagnosis, MG and COVID-19 treatments, HLoS, and mortality at last available follow-up. We reported summary statistics as counts and percentages or mean±SD. When necessary, inverse variance weighting was used to aggregate patient-level data and summary statistics.

Results

Nineteen studies with 152 patients (mean age 54.4 ± 12.7 years; 79/152 [52.0%] female) were included. Hypertension (62/141, 44.0%) and diabetes (30/141, 21.3%) were the most common comorbidities. The mean time between the diagnosis of MG and COVID-19 was7.0 ± 6.3 years. Diagnosis of COVID-19 was confirmed in all patients via RT-PCR tests. Fever (40/59, 67.8%) and ptosis (9/55, 16.4%) were the most frequent COVID-19 and MG symptoms, respectively. Azithromycin and ceftriaxone were the most common COVID-19 treatments, while prednisone and intravenous immunoglobulin were the most common MG treatments. Invasive ventilation treatment was required for 25/59 (42.4%) of patients. The mean HLoS was 18.2 ± 9.9 days. The mortality rate was 18/152 (11.8%).

Conclusion

This report provides an overview of the characteristics, treatment, and outcomes of MG in COVID-19 patients. Although COVID-19 may exaggerate the neurological symptoms and worsens the outcome in MG patients, we did not find enough evidence to support this notion. Further studies with larger numbers of patients with MG and COVID-19 are needed to better assess the clinical outcomes in these patients.

A Diagnostic Dilemma of Dysphonia: A Case Report on Laryngeal Myasthenia Gravis

An autoimmune neuromuscular junction disorder, myasthenia gravis, occurs when antibodies are produced against postsynaptic membrane acetylcholine receptors. Late-onset myasthenia gravis, a rare variant of the disease found in the elderly, has become a diagnostic challenge on account of its atypical presentation. We proffer a case of a 60-year-old man that presented with progressive dysphonia and weakening of cough, which was eventually followed by difficulty in swallowing and nasal regurgitation. Examination and laboratory workup came out unremarkable apart from a positive acetylcholine receptor antibody test, due to which a diagnosis of laryngeal myasthenia, an uncommon presentation of late-onset myasthenia gravis was made. Following treatment with pyridostigmine and prednisolone saw a relief of the active complaints. This article highlights the need for physicians to stay alert and have a high suspicion of such probability for timely diagnosis.

Improving laboratory diagnostics in myasthenia gravis

Introduction: Myasthenia gravis (MG) is a prototypical autoimmune disease, characterized by pathogenic autoantibodies targeting structures of the neuromuscular junction. Radioimmunoprecipitation assays (RIPAs) represent the gold standard for their detection. However, new methods are emerging to complement, or overcome RIPAs, also with the perspective of eliminating the use of radioactive reagents.Areas covered: We discuss advances in laboratory methods, prompted especially by cell-based assays (CBAs), for the detection of the autoantibodies of MG diagnostics, above all those to the nicotinic acetylcholine receptor (AChR), muscle-specific kinase (MuSK), and low molecular-weight receptor-related low-density lipoprotein-4 (LRP4).Expert opinion: CBA technology makes AChRs aggregate on cell membranes, thus allowing to detect autoantibodies to clustered AChRs, with reduction of seronegative MG cases. The diagnostic relevance of RIPA/CBA-measurable LRP4 antibodies is still unclear, in Caucasian patients at least. Live CBAs for the detection of AChR, MuSK, and LRP4 antibodies might represent an alternative to RIPAs, but first require full validation. CBAs could be used as screening tests, limiting RIPAs for antibody quantification. To this end, ELISAs might be an alternative.Fixation procedures preserving enough degree of antigen conformationality could yield AChR and MuSK CBAs suitable for a wide use in clinical-chemistry laboratories.

Intravenous immunoglobulins may prevent prednisone-exacerbation in myasthenia gravis

Corticosteroids may produce a paradoxical worsening of myasthenia gravis (MG) symptoms within the first weeks of treatment. We therefore wanted to assess the hypothesis that a prior infusion of intravenous immunoglobulin (IVIG) may have a protective effect. Our primary objectives were to show that the coadministration of immunoglobulins and glucocorticoids is safe and effective for controlling myasthenic symptoms, and to compare the exacerbation rate with this approach and historical practice without IVIG. We recruited 45 patients with generalized MG who required corticosteroids for the first time and we gave all IVIG before starting the full doses of prednisone. Monitoring was performed with validated scales, questionnaires, and blood tests over a 6-week period. Only 4.4% had severe adverse effects related to IVIG and 86.7% improved clinically. Notably, only 2.2% had a paradoxical symptom exacerbation in the first weeks of starting prednisone, which was statistically lower than the 42% reported in a historical series. We conclude that adjuvant therapy with IVIG when starting prednisone for the first time in patients with generalized MG is safe and effective. Given that the rate of paradoxical worsening was lower than that previously reported, the addition of IVIG may have a protective effect against such exacerbations.

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.

Myasthenic crisis demanding mechanical ventilation: A multicenter analysis of 250 cases

OBJECTIVE

To determine demographic characteristics, clinical features, treatment regimens, and outcome of myasthenic crisis (MC) requiring mechanical ventilation (MV).

METHODS

Analysis of patients who presented with MC between 2006 and 2015 in a German multicenter retrospective study.

RESULTS

We identified 250 cases in 12 participating centers. Median age at crisis was 72 years. Median duration of MV was 12 days. Prolonged ventilation (>15 days) depended on age (p = 0.0001), late-onset myasthenia gravis (MG), a high Myasthenia Gravis Foundation of America Class before crisis (p = 0.0001 for IVb, odds ratio [OR] = infinite), number of comorbidities (>3 comorbidities: p = 0.002, OR 2.99), pneumonia (p = 0.0001, OR 3.13), and resuscitation (p = 0.0008, OR 9.15). MV at discharge from hospital was necessary in 20.5% of survivors. Patients with early-onset MG (p = 0.0001, OR 0.21), thymus hyperplasia (p = 0.002, OR 0), and successful noninvasive ventilation trial were more likely to be ventilated for less than 15 days. Noninvasive ventilation in 92 cases was sufficient in 38%, which was accompanied by a significantly shorter duration of ventilation (p = 0.001) and intensive care unit (ICU) stay (p = 0.01). IV immunoglobulins, plasma exchange, and immunoadsorption were more likely to be combined sequentially if the duration of MV and the stay in an ICU extended (p = 0.0503, OR 2.05). Patients who received plasma exchange or immunoadsorption as first-line therapy needed invasive ventilation significantly less often (p = 0.003). In-hospital mortality was 12%, which was significantly associated with the number of comorbidities (>3) and complications such as acute respiratory distress syndrome and resuscitation. Main cause of death was multiorgan failure, mostly due to sepsis.

CONCLUSION

Mortality and duration of MC remained comparable to previous reports despite higher age and a high disease burden in our study. Prevention and treatment of complications and specialized neurointensive care are the cornerstones in order to improve outcome.

Comparative Outcomes of Respiratory Failure Associated with Common Neuromuscular Emergencies: Myasthenia Gravis versus Guillain-Barré Syndrome

Background and objectives: Myasthenia gravis (MG) and Guillain-Barré Syndrome (GBS) are autoimmune neuromuscular disorders that may present as neuromuscular emergencies requiring mechanical ventilation and critical care. Comparative outcomes of these disease processes, once severe enough to require mechanical ventilation, are not known. In this study, we compared the patients requiring mechanical ventilation in terms of in-hospital complications, length of stay, disability, and mortality between these two disease entities at a national level. Materials and Methods: Mechanically ventilated patients with primary diagnosis of MG (n = 6684) and GBS (n = 5834) were identified through retrospective analysis of Nationwide Inpatient Sample (NIS) database for the years 2006 to 2014. Results: Even though mechanically ventilated MG patients were older (61.0 ± 19.1 versus 54.9 ± 20.1 years) and presented with more medical comorbidities, they had lower disease severity on admission, as well as lower in-hospital complications sepsis, pneumonia, and urinary tract infections as compared with GBS patients. In the multivariate analysis, after adjusting for confounders including treatment, GBS patients had significantly higher disability (odds ratio (OR) 15.6, 95% confidence interval (CI) 10.9-22.2) and a longer length of stay (OR 3.48, 95% CI 2.22-5.48). There was no significant difference in mortality between the groups (8.45% MG vs. 10.0% GBS, p = 0.16). Conclusion: Mechanically ventilated GBS patients have higher disease severity at admission along with more in-hospital complications, length of stay, and disability compared with MG patients. Potential explanations for these findings include delay in the diagnosis, poor response to immunotherapy particularly in patients with axonal GBS variant, or longer recovery time after nerve damage.

[Under-diagnosis of neuromuscular diseases in patients of 80 years and older]

Myasthenia gravis (MG), amyotrophic lateral sclerosis and Guillain-Barre syndrome (GBS) have been classically considered as exceptional or unusual diseases in people with a geriatric profile. Over the past 25 years, several population-based studies have been conducted in the Osona area (Barcelona), which, for the first time, has led to describing the high global incidences in the elderly, especially those over 80 years-old. The results suggest the possibility of underdiagnosis of these neuromuscular diseases in the elderly, a fact that could be especially relevant in the case of MG and GBS, since they are 2potentially reversible entities with high mortality in the event of underdiagnosis and absence of treatment.

New Pathways and Therapeutic Targets in Autoimmune Myasthenia Gravis

Acquired Myasthenia Gravis (MG) is a neuromuscular disease caused by autoantibodies against components of the neuromuscular junction. It is a prototype organ-specific autoimmune disease with well-defined antigenic targets mainly the nicotinic acetylcholine receptor (AChR). Patients suffer from fluctuating, fatigable muscle weakness that worsens with activity and improves with rest.

Various therapeutic strategies have been used over the years to alleviate MG symptoms. These strategies aim at improving the transmission of the nerve impulse to muscle or at lowering the immune system with steroids or immunosuppressant drugs. Nevertheless, MG remains a chronic disease and symptoms tend to persist in many patients, some being or becoming refractory over time. In this review, based on recent experimental data on MG or based on results from clinical trials for other autoimmune diseases, we explore new potential therapeutic approaches for MG patients, going from non-specific approaches with the use of stem cells with their anti-inflammatory and immunosuppressive properties to targeted therapies using monoclonal antibodies specific for cell-surface antigens or circulating molecules.

Incidence of Autoimmune Myasthenia Gravis in a Health Maintenance Organization in Buenos Aires, Argentina

BACKGROUND

Different epidemiological studies, especially in Europe, have estimated the incidence density of myasthenia gravis (MG) to range between 1.7 and 21.3/1,000,000/person-year; however, data from regions such as Latin America are scarce. This study is aimed at estimating the incidence and prevalence of acquired MG in Buenos Aires, Argentina.

METHODS

The study population comprised of affiliates of the Italian Hospital Medical Care Program, a prepaid health maintenance organization located in Buenos Aires. The evaluation method for case detection included a retrospective search from January 1, 2006, through December 31, 2012.

RESULTS

Of the 60 cases identified, 36 (60%) were females. The median age at diagnosis was 69 years (IQR 51.5-79). The mean age at diagnosis was 63.3 years (SD ±20). A total of 28 patients (46.7%) had generalized MG and 32 had ocular MG (53.3%). Thirty five patients (58.3%) had acetylcholine receptor antibodies and 2 (3.3%) had muscle-specific receptor tyrosine kinase antibodies. The crude incidence density (ID) of MG was 61.33 per 1,000,000 person-years (95% CI 47.62-79.99). The adjusted ID for the Argentinean population was 38.8 per 1,000,000 person-years (95% CI 27.09-50.51) and for the Buenos Aires population was 47.49 (95% CI 34.73-60.25).

CONCLUSIONS

The results obtained are similar to those published for other geographical areas.

The Epidemiology of Neuromuscular Diseases

Neuromuscular disorders as a group are linked by anatomy with significant differences in pathogenetic mechanisms, clinical expression, and time course of disease. Each neuromuscular disease is relatively uncommon, yet causes a significant burden of disease socioeconomically. Epidemiologic studies in different global regions have demonstrated certain neuromuscular diseases have increased incidence and prevalence rates over time. Understanding differences in global epidemiologic trends will aid clinical research and policies focused on prevention of disease. There is a critical need to understand the global impact of neuromuscular diseases using metrics currently established for communicable and noncommunicable diseases.

Epidemiology of myasthenia gravis in Northern Portugal: Frequency estimates and clinical epidemiological distribution of cases

INTRODUCTION

In this study we estimated the prevalence, incidence, and mortality of myasthenia gravis (MG) in northern Portugal and characterized the clinical features of the patients identified.

METHODS

We used 2 data sources: clinical records from the hospitals and pyridostigmine prescription registers.

RESULTS

On December 31, 2013, we estimated a point prevalence of 111.7 patients per million population. The highest prevalence was observed in the group >65 years of age, especially in men (288.1 per million). During 2013, we estimated an incidence rate of 6.3 per million per year. Among women, the incidence rate was highest in the 15-49-year age group; in men, incidence increased with age up to 22.1 per million in those >65 years old. The MG-related mortality rate was 0.5 per million.

CONCLUSIONS

These figures are in keeping with similar studies and emphasize the importance of diagnosis and management of MG in elderly populations. Muscle Nerve 54: 413-421, 2016.

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.

Clinical features of patients with Myasthenia gravis from the Henan province, China

INTRODUCTION

Myasthenia gravis (MG) occurs globally, and many studies have indicated that there are regional differences in epidemiology, biomarkers, and prognosis of MG.

METHODS

A total of 478 patients with MG who visited hospitals in the Henan Province between January 2010 and February 2014 were included. Age, gender, age at onset, serum antibody, thymus pathology, treatment information, and Myasthenia Gravis Foundation of America (MGFA) classification were assessed.

RESULTS

Compared with previous reports from other areas, we found some differences in MG patients from Henan. The proportion of childhood MG in our study was lower than other reports of Oriental patients with MG. There seems to be an association between onset age, muscle involvement, and acetylcholine receptor antibody levels. Thymectomy improved the symptoms in 78.5% of thymectomy-treated patients.

CONCLUSIONS

These differences are likely related to geographical, environmental, and ethnic differences. Understanding these differences will help us to define more specific treatment.

Report by the Spanish Foundation for the Brain on the social impact of amyotrophic lateral sclerosis and other neuromuscular disorders

INTRODUCTION

A thorough knowledge of the socioeconomic scope of neuromuscular disease is essential for managing resources and raising social awareness.

DEVELOPMENT

Our group reviewed current data on the epidemiology, mortality and dependence rates, and socioeconomic impact of amyotrophic lateral sclerosis and neuromuscular diseases in Spain. We also recorded how neurological care for these patients is organised.

CONCLUSIONS

Neuromuscular disorders are a very heterogeneous group of diseases, and some are very rare. These disorders account for between 2.8% and 18% of the total motives for a neurological consultation. In Spain, prevalence and incidence figures for amyotrophic lateral sclerosis are similar to those in other countries; however, figures for patients with other neuromuscular diseases are not known. Since the diseases are chronic, progressive, and debilitating, they cause considerable disability and dependence, which in turn directly affects healthcare and social costs associated with the disease. The costs generated by one patient with amyotrophic lateral sclerosis or Duchenne disease have been calculated at about 50 000 euros per year. Neuromuscular disease shows aetiological, diagnostic, and prognostic complexity, and it requires multidisciplinary management. Follow-up for these patients should be entrusted to specialised units.

Life-threatening misdiagnosis of bulbar onset myasthenia gravis as a motor neuron disease: How much can one rely on exaggerated deep tendon reflexes

The autoimmune disease myasthenia gravis (MG), can mimic a variety of neurological disorders leading to a delay in diagnosis and treatment. On occasions, misdiagnosis of MG could lead to unnecessary therapeutic interventions. We report the case of a 50 year-old man, in whom MG was mistaken for motor neuron disease (MND). Subsequently, correct diagnosis and optimal management resulted in saving his life and significant improvement in his functional status. We discuss the importance of considering MG as one of the potential differential diagnoses among cases of new onset or recurrent unexplained bulbar symptoms, despite exaggerated deep tendon reflexes. Also, a literature review on the misdiagnosis of MG and the potential pitfalls in MG diagnosis are discussed.

Prevalence of myasthenia gravis in the Catalan county of Osona

INTRODUCTION

The reported prevalence of myasthenia gravis ranges between 5 and 24 cases per 100,000, and people over 65years account for less than 50% of all cases. The prevalence and clinical characteristics of myasthenia gravis in the county of Osona were studied in patients younger and older than 65.

METHODS

The study draws from the county-based prospective myasthenia gravis register implemented by the Neurology Department at Hospital General de Vic in 1991.

RESULTS

The prevalence of myasthenia gravis was 32.89×10⁵ inhabitants (95%CI, 23.86-41.91). The standardized prevalence (European population) was 35.47×10⁵ inhabitants (95%CI, 26.10-44.84). The ratio of women to men was 1.3. Overall, the group of patients older than 65 accounted for 62.75% of all cases. The prevalence of myasthenia gravis increased considerably in older age groups. No cases were registered among patients under 25years old, prevalence was 21.87×10⁵ in the 25 to 64 age group, and prevalence in patients over 65 years increased to 122.35×10⁵. The clinical characteristics prior to treatment and at the cut-off date are similar (P>.05) in patients younger than 65 and those aged 65 and older.

CONCLUSIONS

These figures show the highest prevalence rate reported to date. This high prevalence is due to the rate observed among patients older than 65. These results provide a new warning that myasthenia gravis may be underdiagnosed in the elderly population.

Myasthenia gravis incidence in a general North Atlantic isolated population

OBJECTIVE

There are no previous studies undertaken about myasthenia gravis in the Faroe Islands. The aim of this study was to establish the incidence of onset of this disease in the Faroese population.

METHOD

Patients were ascertained and registered prospectively from 1986 to 2013 when they were examined at the Neurological Clinic of the Faroese National Hospital or at a private neurological practice, which constitutes all the available neurological services in the Faroe Islands.

RESULT

Twelve new diagnoses were made over a 27-year period, providing an incidence density rate of 9.4 per million person-years (95% confidence limit 4.9-16.5). At presentation, nine of 12 patients had generalized myasthenia gravis and two patients had pure ocular disease, and in one patient, the symptoms were restricted to the bulbo-facial muscles. The sex ratio was 2:1, F/M. In nine of the cases, a positive result of acetylcholine receptor antibody assay was documented. In all patients, there was a beneficial response to anticholinesterase administration.

CONCLUSION

The result yielded no strong evidence of a difference in incidence between that found in the Faroe Islands and those in most European studies, apart from recent studies from London, UK; Norway; Spain, and Italy in which incidences from 21 to 30 per million person-years had been reported.

Undiagnosed myasthenia gravis owing to a very unusual primary presentation

Myasthenia gravis (MG) is an uncommon autoimmune disorder presenting with fluctuating, progressive muscle weakness. The typical initial presentation includes ocular symptoms of ptosis, diplopia, or both. In the literature, other late symptoms have been described. The inability to close the jaws or difficulty in closing the jaws is an uncommon symptom of muscle weakness. Studies have found that only 4% of patients with MG ever complain of, or demonstrate, masticatory muscular weakness with an inability to close the jaws or difficulty in closing the jaws. In the present case, although the patient may have manifested other symptoms, his primary complaint was the inability to masticate as a result of muscular weakness and the difficulty in closing the jaw. The symptoms had reportedly been present for several months. The case is interesting in that the patient presented with an uncommon symptom as the primary complaint. The patient's recall and communication of his medical history was poor, and it is unclear as to all the factors that may have delayed the diagnosis. However, it is important for dentists to recognize these atypical symptoms of MG so that they can either order the initial tests or make the appropriate referral.

Analysis of serum miRNA profiles of myasthenia gravis patients

Myasthenia gravis (MG) is an autoimmune disease characterized by the presence of autoantibodies, mainly against the acetylcholine receptor (AChR). The mechanisms triggering and maintaining this chronic disease are unknown. MiRNAs are regulatory molecules that play a key role in the immune system and are altered in many autoimmune diseases. The aim of this study was to evaluate miRNA profiles in serum of 61 AChR MG patients. We studied serum from patients with early onset MG (n = 22), late onset MG (n = 27) and thymoma (n = 12), to identify alterations in the specific subgroups. In a discovery cohort, we analysed 381 miRNA arrays from 5 patients from each subgroup, and 5 healthy controls. The 15 patients had not received any treatment. We found 32 miRNAs in different levels in MG and analysed 8 of these in a validation cohort that included 46 of the MG patients. MiR15b, miR122, miR-140-3p, miR185, miR192, miR20b and miR-885-5p were in lower levels in MG patients than in controls. Our study suggests that different clinical phenotypes in MG share common altered mechanisms in circulating miRNAs, with no additional contribution of the thymoma. MG treatment intervention does not modify the profile of these miRNAs. Novel insights into the pathogenesis of MG can be reached by the analysis of circulating miRNAs since some of these miRNAs have also been found low in MG peripheral mononuclear cells, and have targets with important roles in B cell survival and antibody production.

Myasthenia gravis: a comprehensive review of immune dysregulation and etiological mechanisms

Autoimmune myasthenia gravis (MG) is characterized by muscle weakness caused by antibodies directed against proteins of the neuromuscular junction. The main antigenic target is the acetylcholine receptor (AChR), but the muscle Specific Kinase (MuSK) and the low-density lipoprotein receptor-related protein (LRP4) are also targets. This review summarizes the clinical and biological data available for different subgroups of patients, who are classified according to antigenic target, age of onset, and observed thymic abnormalities, such as follicular hyperplasia or thymoma. Here, we analyze in detail the role of the thymus in the physiopathology of MG and propose an explanation for the development of the thymic follicular hyperplasia that is commonly observed in young female patients with anti-AChR antibodies. The influence of the pro-inflammatory environment is discussed, particularly the role of TNF-α and Th17-related cytokines, which could explain the escape of thymic T cells from regulation and the chronic inflammation in the MG thymus. Together with this immune dysregulation, active angiogenic processes and the upregulation of chemokines could promote thymic follicular hyperplasia. MG is a multifactorial disease, and we review the etiological mechanisms that could lead to its onset. Recent global genetic analyses have highlighted potential susceptibility genes. In addition, miRNAs, which play a crucial role in immune function, have been implicated in MG by recent studies. We also discuss the role of sex hormones and the influence of environmental factors, such as the viral hypothesis. This hypothesis is supported by reports that type I interferon and molecules mimicking viral infection can induce thymic changes similar to those observed in MG patients with anti-AChR antibodies.

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.

[Myasthenia gravis and autoantibodies: Pathophysiology of the different subtypes]

Myasthenia gravis is characterized by muscle weakness and abnormal fatigability. It is an autoimmune disease caused by the presence of antibodies against components of the muscle membrane localized at the neuromuscular junction. In most cases, the autoantibodies are directed against the acetylcholine receptor (AChR). Recently, other targets have been described, such as muscle-specific kinase protein (MuSK) or lipoprotein related protein 4 (LRP4). The origin of the autoimmune response is not known, but thymic abnormalities and defects in immune regulation certainly play a major role in patients with anti-AChR antibodies. Genetic predisposition probably influences the occurrence of the disease. Sex hormones seem to play a role in the early form of the disease. Muscle weakness is fluctuating and worsens with exercise. Myasthenia gravis could be classified according to the location of the affected muscles (ocular versus generalized), the age of onset of symptoms, thymic abnormalities and profile of autoantibodies. These criteria are used to optimize the management and treatment of patients. In this review, we analyze the latest concepts of the pathophysiology of myasthenia gravis according to the different subgroups of the disease, including a description of the role of immunological, genetic and environmental factors. The potential viral hypothesis of this disease is discussed. Finally, we also discuss the biological assays available to validate the diagnosis.

Different characteristic phenotypes according to antibody in myasthenia gravis

OBJECTIVES

To find the characteristic phenotypes of 3 different types of myasthenia gravis (MG).

METHODS

The clinical and electrophysiological features among 15 cases of muscle-specific kinase antibody positive (MuSK Ab+) MG, 59 cases of double seronegative (DSN) MG, and 161 cases of acetylcholine receptor antibody (AChR Ab)+ MG in the University of Alabama at Birmingham were compared.

RESULTS

AChR Ab was positive in 69% of cases and MuSK Ab in 6% of cases. MuSK Ab+ MG was more common (14%) in African Americans compared with whites (4%). AChR Ab+ MG is characterized by male predominance, later onset, a fewer cases of ocular MG, and a higher association with thymoma. DSN-MG is characterized by a greater prevalence of ocular MG, milder forms of MG with less number of crisis, and fewer abnormalities in the repetitive nerve stimulation test. MuSK Ab+ MG is characterized by younger age at onset, severe and bulbar forms of MG, predominant faciobulbar neck weakness, and a poor response to edrophonium, anticholinesterase, and intravenous immunoglobulin. Long-term outcome showed no difference among 3 types of MG.

CONCLUSIONS

AChR Ab+ MG and DSN-MG are similar, with the exception of less severity in the latter. MuSK Ab+ MG has distinct clinical and electrophysiological features.

A cohort study on myasthenia gravis patients in China

Clinical classification and age distribution in myasthenia gravis (MG) cases seem different between Oriental and Caucasian populations, but there have rarely been any clinical studies on MG patients from mainland China. The goal of the current study was to perform a comprehensive survey of myasthenia gravis in a hospital in China, establishing contemporary cohort data and clinical features. 1,108 unselected patients with MG attending the 309th Hospital of PLA, Beijing, China were studied during a 36-month period from July 2008 to June 2011. The sex ratio was 1:1 (F:M). 62.5 % of patients presented as adolescents and adults. Ocular MG cases accounted for 65.6 % childhood MG patients. A positive response was observed in 96.8 % of the patients for neostigmine tests, whereas a positive decremental response to low frequency repetitive nerve stimulation (RNS) was observed in 77.4 % of the patients. The highest stimulating positive rate was 65.3 % in stimulated facial nerve. Thymoma was significantly increased in those patients with severe MG, especially in the cohort involving the respiratory muscles (p < 0.001). The study revealed higher frequency of ocular and childhood MG compared to other studies in USA and European countries, which can be a result of optimum case ascertainment, increased disease duration, or application of complex diagnostic tests. The relative increase in the prevalence of ocular myasthenia can be attributed to the impact of an aging population.

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.

Myasthenia gravis: sleep quality, quality of life, and disease severity

INTRODUCTION

There is much research on quality of life in myasthenia gravis (MG), and its relationship to disease severity is well-established. However, evidence regarding sleep disturbance in MG is inconclusive.

METHODS

To evaluate sleep and quality of life among clinically stable MG patients, 54 subjects were investigated by means of the Pittsburgh Sleep Quality Index (PSQI), Epworth Sleepiness Scale (ESS) and 15-Item-Quality-Of-Life Instrument for MG (MG-QOL15).

RESULTS

A pathological PSQI score, which was observed in 59% of patients, was increased in subjects with active disease compared with patients in clinical remission [odds ratio = 4.3; confidence interval 95% (1.0-17.6); P = 0.04]. We found a relationship between PSQI and MG-QOL15 scores in patients with clinically active disease (r = 0.62; P < 0.001).

CONCLUSIONS

Our study highlights the high prevalence of sleep disturbance among MG patients. Disease severity may be considered to be a MG-specific risk factor for patient-reported sleep disturbance. The MG-QOL15 and PSQI should be used to estimate the impact of the disease on sleep and quality of life.

[Is myasthenia gravis overlooked in the over-80s? Two case reports]

Myasthenia gravis (MG) is diagnosed more often today than previously. The increase is mainly found in patients over the age of 60 years. Recent data indicate that MG may still be substantially underdiagnosed in very old people. We report two cases of MG in elderly women, in whom the initial diagnosis was uncertain. When faced with new onset of weakness in an elderly patient, particularly of cranial musculature, clinicians should consider MG as a diagnostic possibility.