Myasthenia Gravis

Correlation Between Thymus Radiology and Myasthenia Gravis in Clinical Practice

Background: The ability to distinguish between a normal thymus, thymic hyperplasia, and thymoma should aid in clinical management and decision making for patients with myasthenia gravis (MG). We sought to determine the accuracy of routine radiological examinations in predicting thymic pathology.

Methods: We retrospectively analyzed the records of patients with MG who had undergone thymectomy from the Second Affiliated Hospital of Zhengzhou University. Each patient received at least one initial radiological diagnosis and one histological diagnosis, and the patients were classified into the all-patient, CT, contrast CT, and MRI groups. The sensitivity, accuracy and specificity of each group were calculated for different histological types.

Results: This study included 114 patients. All sensitivity, specificity and accuracy values except for sensitivity to hyperplasia in each group for different histological types were satisfactory. MRI had higher sensitivity (68.4, 95% CI: 43.5–87.4%) to histological hyperplasia than did CT (14.3, 95% CI: 0.4–57.9%) and contrast CT (26.7, 95% CI: 7.8–55.1%). Contrast CT had higher specificity (97.9, 95% CI: 88.9–99.95%) for histological hyperplasia than did MRI (88.5, 95% CI: 69.9–97.6%).

Discussion: For patients with MG, CT, contrast CT, and MRI examinations can effectively identify thymoma. Additionally, compared with CT or contrast CT, MRI may have a stronger ability to distinguish thymoma and detect hyperplasia.

Inflammatory myopathy with myasthenia gravis: Thymoma association and polymyositis pathology

Objective

To provide evidence that idiopathic inflammatory myopathy (IM) with myasthenia gravis (MG) frequently shows thymoma association and polymyositis (PM) pathology and shares clinicopathologic characteristics with IM induced by immune checkpoint inhibitors (ICIs).

Methods

We analyzed the clinicopathologic features of 10 patients with idiopathic IM and MG identified in 970 consecutive patients with biopsy-proven IM.

Results

Seven patients (70%) had thymoma. IM and MG were diagnosed with more than 5-year time difference in 6 thymomatous patients and within 1 year in 1 thymomatous and 3 nonthymomatous patients. Seven thymomatous patients showed rhabdomyolysis-like features with respiratory failure (4/7), dropped head (3/7), cardiac involvement (2/7), and positive anti-acetylcholine receptor (anti-AChR) and anti-titin antibodies (7/7 and 4/6, respectively) but rarely showed ocular symptoms (2/7) or decremental repetitive nerve stimulation (RNS) responses (1/7) at IM diagnosis. Three nonthymomatous patients showed acute cardiorespiratory failure with rhabdomyolysis-like features (1/3), positive anti-AChR and anti-titin antibodies (3/2 and 2/2, respectively), and fluctuating weakness of the skeletal muscle without ocular symptoms (3/3). Muscle pathology showed a PM pathology with infiltration of CD8-positive CD45RA-negative T-lymphocytes (9/9), scattered endomysial programmed cell death 1 (PD-1)-positive cells (9/9), and overexpression of programmed cell death ligand 1 (PD-L1) on the sarcolemma of muscle fibers around the infiltrating PD-1-positive cells (7/9).

Conclusion

Rhabdomyolysis-like features, positive anti-AChR antibody without decremental RNS responses, and PD-L1 overexpression are possible characteristics shared by ICI-induced IM. Frequent thymoma association in patients with idiopathic IM and MG may suggest thymoma-related immunopathogenic mechanisms, including dysregulation of the immune checkpoint pathway.

Ocular myasthenia gravis: an update on diagnosis and treatment

PURPOSE OF REVIEW

Myasthenia gravis is an autoimmune disease that commonly affects the palpebral and extraocular muscles. Ocular myasthenia gravis (OMG) is a variant of the disease that is confined to the ocular muscles but frequently becomes generalized over time. The diagnosis of OMG is often challenging but both clinical and laboratory findings are helpful in confirming the clinical suspicion. This review provides an update on the diagnostic approach and therapeutic options for OMG.

RECENT FINDINGS

Antimuscle-specific tyrosine kinase and LDL-related receptor-related protein 4 are newly available serologic testing for myasthenia gravis that can help in increasing the diagnostic sensitivity of OMG. They should be included to the diagnostic algorithm of OMG in appropriate clinical situations.

SUMMARY

OMG remains a primarily clinical diagnosis, but recent advances in laboratory testing can improve the diagnostic accuracy and should be used in appropriate clinical settings. The mainstay of treatment for OMG has not significantly changed over the past years, but the increasing availability of steroid-sparing agents improved the disease control while minimizing steroid-induced complications.

Amifampridine phosphate in the treatment of muscle-specific kinase myasthenia gravis: a phase IIb, randomized, double-blind, placebo-controlled, double crossover study

Objective:

The aim of this study is to determine the safety and the efficacy of amifampridine phosphate in muscle-specific kinase antibody-positive myasthenia gravis, in a 1:1 randomized, double-blind, placebo-controlled, switchback, double crossover study.

Methods:

Eligible patients had muscle-specific kinase myasthenia gravis, >18 years of age, and Myasthenia Gravis Foundation of America class II–IV with a score of ⩾9 on Myasthenia Gravis Composite scale. After the run-in phase, during which amifampridine phosphate was titrated to a tolerable and effective dosage, patients were randomized to receive placebo–amifampridine–placebo sequence or amifampridine–placebo–amifampridine sequence daily for 7 days. Then, patients switched treatment arms twice, for a total of 21 days of double-blind treatment. Safety was determined by serial assessments of adverse events/serious adverse events, physical examinations, and clinical and laboratory tests. The co-primary outcome measures included changes from baseline of Quantitative Myasthenia Gravis score and Myasthenia Gravis–specific Activities of Daily Living Profile score. The secondary outcome measures comprised changes from baseline of Myasthenia Gravis Composite score, Myasthenia Gravis Quality of Life scale—15 questions, Fatigue Severity Scale, and Carlo Besta Neurological Institute–Myasthenia Gravis scale. Statistical analyses were assessed using a switchback model for three-period, two-treatment crossover design.

Results:

A total of 10 patients were screened, enrolled, and treated. Transient paresthesias (60%) were the only amifampridine phosphate–related adverse events reported. Four patients were randomized to receive placebo–amifampridine–placebo sequence and three patients to receive amifampridine–placebo–amifampridine sequence. The co-primary objectives were statistically met (Quantitative Myasthenia Gravis score: p = 0.0003 and Myasthenia Gravis–specific Activities of Daily Living Profile score: p = 0.0006), as well as all the secondary endpoints (Myasthenia Gravis Composite score: p < 0.0001, Myasthenia Gravis Quality of Life scale—15 questions: p = 0.0025, Fatigue Severity Scale: p = 0.0061, and Carlo Besta Neurological Institute–Myasthenia Gravis scale: p = 0.0014).

Conclusion:

Despite the low number of patients, MuSK-001 study provided evidence that amifampridine phosphate, in the range of 30–60 mg daily dose, was safe and effective in treating muscle-specific kinase myasthenia gravis, suggesting the need for a large multi-center trial to confirm these results.

Circulating microRNA plasma profile in MuSK+ myasthenia gravis

Muscle-specific tyrosine kinase antibody positive myasthenia gravis (MuSK+ MG) is an immunological subtype with distinctive pathogenic mechanisms and clinical features. The aim of this study was to analyze the circulating plasma microRNA profile of patients with MuSK+ MG. From the discovery cohort miR-210-3p, miR-324-3p and miR-328-3p were further analyzed in the validation cohort. We found a distinct plasma profile of miR-210-3p and miR-324-3p that were significantly decreased in MuSK+ MG patients compared to healthy controls (4.1 ± 1.4 vs 5.1 ± 1.4, p = .006 and 4.7 ± 1.0 vs 5.4 ± 1.3, p = .02). These findings reveal a distinct plasma miRNA profile in MuSK+ MG.

What is in the Neuromuscular Junction Literature?

This update begins with myasthenia gravis and the roles of anti-agrin and cortactin antibodies. Regarding diagnosis, a report on repeated ice pack testing is highlighted as are several reports on the close correlation of electrodiagnostic testing with clinical features and the response to treatment. The incidence of head drop and associated clinical and ventilatory features are gleaned from a retrospective study. We also discuss a study that assessed the predominantly symmetric and conjugate ocular findings in MuSK-myasthenia gravis. Other topics that are covered include quality of life and preoperative risk. We then summarize the positive treatment trials of subcutaneous immunoglobulin and eculizumab. Turning to Lambert-Eaton Myasthenic Syndrome, we report on an epidemiologic study performed on the veteran affairs population, the results of the DAPPER study of 3, 4 diaminopyridine, and look to the future for other treatment options involving calcium gating modifiers.

Associations between autoimmune conditions and hepatobiliary cancer risk among elderly US adults

Growing evidence suggests that people with autoimmune conditions may be at increased risk of hepatobiliary tumors. In the present study, we evaluated associations between autoimmune conditions and hepatobiliary cancers among adults aged ≥66 in the United States. We used Surveillance, Epidemiology, and End Results (SEER)-Medicare data (1992-2013) to conduct a population-based, case-control study. Cases (n = 32,443) had primary hepatobiliary cancer. Controls (n = 200,000) were randomly selected, cancer-free adults frequency-matched to cases by sex, age and year of selection. Using multivariable logistic regression, we calculated odds ratios (ORs) and 95% confidence intervals (CIs) for associations with 39 autoimmune conditions identified via Medicare claims. We also conducted separate analyses for diagnoses obtained via inpatient versus outpatient claims. Sixteen conditions were associated with at least one hepatobiliary cancer. The strongest risk estimates were for primary biliary cholangitis with hepatocellular carcinoma (OR: 31.33 [95% CI: 23.63-41.56]) and primary sclerosing cholangitis with intrahepatic cholangiocarcinoma (7.53 [5.73-10.57]), extrahepatic cholangiocarcinoma (5.59 [4.03-7.75]), gallbladder cancer (2.06 [1.27-3.33]) and ampulla of Vater cancer (6.29 [4.29-9.22]). Associations with hepatobiliary-related conditions as a group were observed across nearly all cancer sites (ORs ranging from 4.53 [95% CI: 3.30-6.21] for extrahepatic cholangiocarcinoma to 7.18 [5.94-8.67] for hepatocellular carcinoma). Restricting to autoimmune conditions diagnosed via inpatient claims, 6 conditions remained associated with at least one hepatobiliary cancer, and several risk estimates increased. In the outpatient restricted analysis, 12 conditions remained associated. Multiple autoimmune conditions are associated with hepatobiliary cancer risk in the US Medicare population, supporting a shared immuno-inflammatory etiology to these cancers.

Mycophenolic acid in patients with immune-mediated inflammatory diseases: From humans to dogs

Mycophenolic acid (MPA), a noncompetitive, selective and reversible inhibitor of inosine 5'-monophosphate dehydrogenase (IMPDH), is an immunosuppressive agent that has a long history in medicine. Mechanistically, the inhibition of IMPDH leads to the selective and eventual arrest of T- and B-lymphocyte proliferation. Mycophenolate mofetil (MMF), the first MPA-based product to receive marketing approval over two decades ago, was originally indicated for the prophylaxis of organ rejection in human transplant patients. Given its broad immunosuppressive properties and ability to selectively inhibit lymphocyte division and effector functions, the clinical utility of MPA was subsequently explored in a host of autoimmune diseases. Human clinical studies have shown MPA to be safe and effective and support its off-label administration for immune-mediated diseases such as lupus, myasthenia gravis and atopic dermatitis. MMF became generically available in the United States in 2008, and its clinical utility is increasingly being explored as a treatment option for dogs with immune-mediated diseases. This review summarizes the available literature for MPA pharmacokinetics and pharmacodynamics, and the current status of MPA as a treatment for client-owned dogs diagnosed with immune-mediated diseases.

Juvenile Ocular Myasthenia Gravis: Presentation and Outcome of a Large Cohort

BACKGROUND

Isolated ocular myasthenia gravis (MG) is sparingly common in children relative to adults, ranging from 71% to 93% of all children with MG.

PURPOSE

We aimed to characterize the ocular manifestations and outcomes in children with isolated ocular MG.

METHODS

Medical records of consecutive 62 subjects less than 15 years of age with ocular MG, were retrospectively reviewed. Demographic data, presenting ocular features, types and variabilities of duction limitation, MG confirmatory tests, types of and responses to treatment, and generalized MG conversion were reviewed.

RESULTS

Mean age at onset and follow-up time were 49 months (range, one to 173 months) and 95 months (range, six to 226 months), respectively. Female-to-male ratio was 1.5:1. Initially, ptosis was found in 60 subjects (96.8%), while duction limitation was observed in 28 subjects (45.2%). Total ophthalmoparesis was the most common type of duction limitation. Variability of duction limitation was found in 68% of subjects during the follow-up. Pyridostigmine alone was the most common medication used (48.4%); ptosis was more responsive to therapy than duction limitation. Conversion to generalized MG occurred in 19.4% of subjects, with a mean interval to conversion of nine months after symptom onset. Most conversions (91.7%) occurred in the first two years.

CONCLUSIONS

Ptosis was more responsive to treatment than duction limitation. Thus other treatment modalities, as well as strabismic amblyopia screening, should be considered in children with prolonged duction limitation that is refractory to medication. In contrast with adults, a much lower proportion of children converted to generalized MG. This may explain the higher prevalence of isolated ocular MG among the juvenile population.

Maternal myasthenia gravis represents a risk for the child through autoantibody transfer, immunosuppressive therapy and genetic influence

Females with myasthenia gravis (MG) worry about their disease having negative consequences for their children. Autoimmune disease mechanisms, treatment and heredity could all have an impact on the child. This is a subject review where Web of Science was searched for relevant keywords and combinations. Controlled and prospective studies were included, and also results from selected and unselected patient cohorts, guidelines, consensus papers and reviews. Neonatal MG with temporary muscle weakness occurs in 10% of newborn babies where the mother has MG, due to transplacental transfer of antibodies against acetylcholine receptor (AChR), muscle-specific kinase (MuSK) or lipoprotein receptor-related protein 4 (LRP4). Arthrogryposis and fetal AChR inactivation syndrome with contractures and permanent myopathy are rare events caused by mother's antibodies against fetal type AChR. The MG drugs pyridostigmine, prednisolone and azathioprine are regarded as safe during pregnancy and breastfeeding. Methotrexate, mycophenolate mofetil and cyclophosphamide are teratogenic. Mother's MG implies at least a 10-fold increased risk for MG and other autoimmune diseases in the child. MG females should receive specific information about pregnancy and giving birth. First-line MG treatments should usually be continued during pregnancy. Intravenous immunoglobulin and plasma exchange represent safe treatments for exacerbations. Neonatal MG risk means that MG women should give birth at hospitals experienced in neonatal intensive care. Neonatal MG needs supportive care, rarely also acetylcholine esterase inhibition or intravenous immunoglobulin. Women with MG should be supported in their wish to have children.

Effects of long-term respiratory muscle endurance training on respiratory and functional outcomes in patients with Myasthenia gravis

BACKGROUND

Myasthenia gravis (MG) is characterized by reduced muscle endurance and often leads to respiratory complications.

OBJECTIVE

A long-term respiratory muscle endurance training (RMET) based on normocapnic hyperpnea was introduced for the first time in MG patients. We investigated RMET effects on respiratory endurance (RE), MG symptoms, lung function and physical fitness and compared the results with a control group (CG).

METHODS

The training period consisted of four weeks intensive training (IT; five 30-min training sessions per week) followed by twelve months maintenance training (MT; five 30-min training sessions over two weeks). Eighteen patients with mild to moderate MG participated as the training group (TG), six patients served as CG. RE, lung function, MG score and physical fitness were tested before and after IT and after three to twelve months of MT.

RESULTS

Only 12 TG patients completed the entire training period. Thirteen months of training significantly increased RE measured as time until exhaustion (T_lim) to 412% of baseline (P < 0.001). The MG score improved from 0.67±0.09 to 0.41 ± 0.1 (p = 0.004), and the number of squats per minute as a measure of physical fitness increased in the TG to 160% of baseline (p = 0.015). While lung function did not change during the training period, we observed a modulation in the breathing pattern at rest with prolonged expiration (122% of baseline, p = 0.028). In addition, TG reported subjective improvements in MG symptoms, respiratory symptoms and physical fitness by 49%, 58% and 64%, respectively (P < 0.001). No significant changes were observed in the CG.

CONCLUSION AND SIGNIFICANCE

This is the first controlled long-term RMET study in MG patients. The results demonstrated that this normocapnic hyperpnea training is feasible and beneficial for patients with mild to moderate MG and is a valuable supplement to conventional drug treatment.

HLA and MuSK-positive myasthenia gravis: A systemic review and meta-analysis

OBJECTIVES

Myasthenia gravis (MG) represents a spectrum of clinical subtypes with differences in disease mechanisms and treatment response. MG with muscle-specific tyrosine kinase (MuSK) antibodies accounts for 1%-10% of all MG patients. We conducted a meta-analysis to evaluate the association between HLA genes and MuSK-MG susceptibility.

SUBJECTS AND METHODS

Studies were searched in Pubmed, EMBASE database and other sources between 2001 and 2018. Genotype, allele and haplotype frequencies of HLA loci in MuSK-MG patients and healthy controls were extracted from each included study.

RESULTS

The meta-analysis showed that HLA DQB1*05, DRB1*14 and DRB1*16 were strongly associated with an increased risk of MuSK-MG (P < .0001), whereas HLA DQB*03 was less frequent in MuSK patients compared with healthy controls (P < .05). Haplotype analysis showed that these DQB1 and DRB1 alleles were closely linked, forming both risk (DQ5-DR14, DQ5-DR16, P < .0001) and protective (DQ3-DR4, DQ3-DR11, P < .05) haplotypes.

CONCLUSION

The distinct genetic patterns of MuSK-MG indicate that variation in HLA class II genes plays an important role in the pathogenesis of MuSK-MG patients.

Myasthenia gravis imitating pituitary apoplexy in macroprolactinoma

Myasthenia gravis (MG) is an autoimmune disease affecting neuromuscular transmission that manifests with muscle weakness and typically involves the eye muscles, often producing diplopia and ptosis. Recent studies suggest that hyperprolactinaemia may have a role in the development of MG, although its association with prolactinoma is extremely rare. We report the unusual case of a 71-year-old male affected with macroprolactinoma, who presented at our Center 2 weeks after starting cabergoline treatment because of acute onset of headache, diplopia, and ptosis. On admission, he presented with drowsiness, dropped head, swallowing impairment and bilateral ptosis, which rapidly worsened. Based on clinical manifestation and history, emergency surgery was performed on suspicion of pituitary apoplexy (PA), the typical complication occurring in patients with macroadenomas who present these symptoms. No pituitary haemorrhage was found. The symptoms initially resolved after surgery, but soon returned and worsened day by day, especially in the evening, despite the increase of cortisone replacement doses. MG was thus suspected and confirmed by the detection of antibodies to the acetylcholine receptor. Pyridostigmine was started with prompt improvement of neurological symptoms. In conclusion, although very rare, MG should be considered in the differential diagnosis of patients with macroprolactinomas and suggestive neurological symptoms in order to provide early and appropriate treatment. The role of hyperprolactinaemia in MG onset and evolution is also discussed.

The impact of physical exercise on neuromuscular function in Myasthenia gravis patients: A single-subject design study

There is a need for tailored exercise recommendations to patients with Myasthenia gravis (MG). A few pilot studies have recently shown that physical exercise in accordance with general recommendations to healthy adults can be applied safely to patients with mild MG symptoms. How physical exercise affects muscle parameters and risk factors for lifestyle diseases in patients with MG is, however, only poorly known. We evaluated functional skeletal muscle parameters in 11 MG patients, before and after conducting a 12-week supervised physical therapy regimen of aerobic and resistance strength training. After the training program, parameters of the rectus femoris muscle improved: compound motor action potential (from 4.5 ± 2.6 to 5.3 ± 2.8 mV, P = .016), isometric muscle force (from 25.2 ± 4.4 to 30.2 ± 3.8 kg; P = .014), and ultrasound muscle thickness (from 19.6 ± 5.6 to 23.0 ± 3.9 mm, P = .0098) all increased. Further, physical performance based measures improved, including the 30-Second Chair Stand Test (median change +2, P = .0039) as well as the clinical MG composite score [from 3 (2-5) to 2 (0-4), P = .043]. No improvement in muscle function was observed in the biceps brachii muscle. These findings indicate that MG patients can improve their muscular functions by incorporating aerobic and resistance strength training, especially in proximal leg muscles. This is important knowledge when physical therapy is considered for this patient group, for whom no guidelines on physical exercise currently exist.

Myasthenia Gravis and Thymoma Surgery: A Clinical Update for the Cardiothoracic Anesthesiologist

Myasthenia gravis (MG) is a rare neuromuscular disorder characterized by skeletal muscle weakness. Patients with MG who have thymoma and thymic hyperplasia have indications for thymectomy. The perioperative care of patients with MG scheduled for thymus resection should be focused on optimizing their neuromuscular function, identifying factors related to postoperative mechanical ventilation, and avoiding of triggers associated with myasthenic or cholinergic crisis. Minimally invasive surgical techniques, use of regional analgesia, and avoidance or judicious administration of neuromuscular blocking drugs (NMBs) is recommended during the perioperative period. If NMBs are used, sugammadex appears to be the drug of choice to restore adequately the neuromuscular transmission. In patients with postoperative myasthenic crisis, plasma exchange or intravenous immune globulin and mechanical support is recommended.

T Follicular Helper Cells in Autoimmune Disorders

T follicular helper (Tfh) cells are a distinct subset of CD4⁺ T lymphocytes, specialized in B cell help and in regulation of antibody responses. They are required for the generation of germinal center reactions, where selection of high affinity antibody producing B cells and development of memory B cells occur. Owing to the fundamental role of Tfh cells in adaptive immunity, the stringent control of their production and function is critically important, both for the induction of an optimal humoral response against thymus-dependent antigens but also for the prevention of self-reactivity. Indeed, deregulation of Tfh activities can contribute to a pathogenic autoantibody production and can play an important role in the promotion of autoimmune diseases. In the present review, we briefly introduce the molecular factors involved in Tfh cell formation in the context of a normal immune response, as well as markers associated with their identification (transcription factor, surface marker expression, and cytokine production). We then consider in detail the role of Tfh cells in the pathogenesis of a broad range of autoimmune diseases, with a special focus on systemic lupus erythematosus and rheumatoid arthritis, as well as on the other autoimmune/inflammatory disorders. We summarize the observed alterations in Tfh numbers, activation state, and circulating subset distribution during autoimmune and some other inflammatory disorders. In addition, central role of interleukin-21, major cytokine produced by Tfh cells, is discussed, as well as the involvement of follicular regulatory T cells, which share characteristics with both Tfh and regulatory T cells.

Advances in autoimmune myasthenia gravis management

INTRODUCTION

Myasthenia gravis (MG) is an autoimmune neuromuscular disorder with no cure and conventional treatments limited by significant adverse effects and variable benefit. In the last decade, therapeutic development has expanded based on improved understanding of autoimmunity and financial incentives for drug development in rare disease. Clinical subtypes exist based on age, gender, thymic pathology, autoantibody profile, and other poorly defined factors, such as genetics, complicate development of specific therapies. Areas covered: Clinical presentation and pathology vary considerably among patients with some having weakness limited to the ocular muscles and others having profound generalized weakness leading to respiratory insufficiency. MG is an antibody-mediated disorder dependent on autoreactive B cells which require T-cell support. Treatments focus on elimination of circulating autoantibodies or inhibition of effector mechanisms by a broad spectrum of approaches from plasmapheresis to B-cell elimination to complement inhibition. Expert commentary: Standard therapies and those under development are disease modifying and not curative. As a rare disease, clinical trials are challenged in patient recruitment. The great interest in development of treatments specific for MG is welcome, but decisions will need to be made to focus on those that offer significant benefits to patients.

Cholinesterases and the fine line between poison and remedy

Acetylcholinesterase (AChE, EC 3.1.1.7) and butyrylcholinesterase (BChE, EC 3.1.1.8) are related enzymes found across the animal kingdom. The critical role of acetylcholinesterase in neurotransmission has been known for almost a century, but a physiological role for butyrylcholinesterase is just now emerging. The cholinesterases have been deliberately targeted for both therapy and toxicity, with cholinesterase inhibitors being used in the clinic for a variety of disorders and conversely for their toxic potential as pesticides and chemical weapons. Non-catalytic functions of the cholinesterases (ChEs) participate in both neurodevelopment and disease. Manipulating either the catalytic activities or the structure of these enzymes can potentially shift the balance between beneficial and adverse effect in a wide number of physiological processes.

Oral Immunosuppressive Treatment of Myasthenia Gravis in Denmark: A Nationwide Drug Utilization Study, 1996-2013

Although immunosuppressants in the treatment of myasthenia have been available for several decades, population-based studies describing drug utilization in myasthenia patients are scarce. We aimed in this study to describe the treatment of myasthenia in Denmark in more recent years with emphasis on use of oral immunosuppressant agents. We identified a nationwide cohort of incident myasthenia patients in Denmark from 1996 to 2013 and tracked their use of drugs over the entire period using data from nationwide registers. Patients with myasthenia were classified according to utilization of specific immunosuppressants (e.g. prednisolone) as 'never user' or 'ever user'. We used Kaplan-Meier (K-M) and proportion of patients covered (PPC) curves to describe treatment onset and termination. We identified 928 patients (52% female) with incident myasthenia in the study period. Overall, 638 (69%) were treated with prednisolone and 506 (55%) with azathioprine. Treatment with prednisolone and azathioprine within 2 years of myasthenia diagnosis was initiated in 462 (56%) and 366 (45%). Only one of four myasthenia patients (n = 231) did not receive oral immunosuppressive treatment at any time in the study period. Prednisolone was stopped in most patients, whereas treatment with azathioprine was often continued throughout follow-up. In conclusion, we found that treatment of myasthenia in Denmark in recent years corresponded well to the expected clinical course of myasthenia and that most patients underwent long-term immunosuppression.

Myasthenia Gravis With Thymoma, Manifesting as AChR-Ab-Positive, Distinct Bulbar Palsy Accompanied by Dysgeusia: A Case Series and Review of Literature

In this review, we summarized three cases of myasthenia gravis (MG) with taste disorder and describe their clinical features in detail. Three MG patients presented with significant bulbar palsy symptoms, high AChR-Ab titers, and negative MuSK-Ab, were diagnosed with thymoma. Furthermore, we observed that dysgeusia could manifest earlier than the occurrence of typical MG symptoms, even predict a MG relapse or a myasthenic crisis in the course of MG. We believe that dysgeusia is a non-motor symptom of MG, which especially exists in MG patients with thymoma and serious bulbar palsy. Therefore, being alert to this symptom may facilitate the early diagnosis of MG and judge the progress of the disease.

A patient with weakness and an abnormal chest radiograph: A case report

A 40-year-old black male presented to ICU after intubation for airway protection due to rapid onset of neck weakness and swallowing difficulty. His chest radiograph showed an unusual mediastinal opacity for which a computer tomography (CT) scan was done, confirming a mediastinal mass.

Serological Immunoglobulin-Free Light Chain Profile in Myasthenia Gravis Patients

Background

Serological levels of free immunoglobulin light chains (FLCs), produced in excess of heavy chains during synthesis of immunoglobulins by plasma cells, can be considered a direct marker of B cell activity in different systemic inflammatory-autoimmune conditions and may represent a useful predictor of rituximab (RTX) therapeutic efficacy, as reported for rheumatoid arthritis and systemic lupus erythematosus. Myasthenia gravis (MG) is an autoimmune disease of the neuromuscular junction with antibodies (abs) targeting the acetylcholine receptor (AChR) or the muscle-specific tyrosine kinase (MuSK), inducing muscle weakness and excessive fatigability. As MG course may be remarkably variable, we evaluated the possible use of FLCs as biomarkers of disease activity.

Subjects and Methods

We assessed FLC levels in 34 sera from 17 AChR-MG and from 13 MuSK-MG patients, in comparison with 20 sera from patients with systemic autoimmune rheumatic diseases and 18 from healthy blood donors, along with titers of specific auto-abs and IgG subclass distribution.

Results

We found a statistically significant increase in free κ chains in both AChR- and MuSK-MG patients, while free λ chain levels were increased only in AChR-MG. We also observed a significant reduction of both free κ and λ chains in 1/4 MuSK-MG patients along with specific abs titer, two months after RTX treatment.

Conclusions

From our data, FLCs appear to be a sensitive marker of B cell activation in MG. Further investigations are necessary to exploit their potential as reliable biomarkers of disease activity.

Myasthenia Gravis and Associated Diseases

BACKGROUND:

Myasthenia gravis (MG) is an autoimmune disease caused by the action of specific antibodies to the postsynaptic membrane of the neuromuscular junction, leading to impaired neuromuscular transmission. Patients with MG have an increased incidence of other autoimmune diseases.

AIM:

to determine the presence of other associated diseases in patients with MG.

METHOD:

A group of 127 patients with MG followed in 10 years period, in which the presence of other associated diseases has been analysed.

RESULTS:

The sex ratio is in favour of the female sex, the average age of the initial manifestation of the disease is less than 50 years, 65.4% of the patients with MG have another disease. 15.0% patients have associated another autoimmune disease. Thyroid disease is the most common associated with MG, rarely rheumatoid arthritis (RA), systemic lupus erythematosus (SLE) and other autoimmune diseases. Other diseases include hypertension, heart disease, diabetes, respiratory diseases, dyslipidemia. 10.2% of the patients are diagnosed with extrathymic tumours of various origins.

CONCLUSION:

Associated diseases are common in patients with MG, drawing attention to the possible common basis for their coexistence, as well as their impact on the intensity and treatment of the disease.

Thymectomy lowers the myasthenia gravis biomarker miR-150-5p

Objective

The aim of the study was to analyze the effect of thymectomy on the proposed disease-specific microRNA (miRNA) biomarkers miR-150-5p and miR-21-5p in patients from the prospective randomized trial of thymectomy in myasthenia gravis (MGTX trial) and to evaluate the longitudinal changes in clinical patterns compared with these miRNA levels.

Methods

Serum samples were obtained from 80 patients with MG who were included in the MGTX trial. Thirty-eight patients were randomized to thymectomy plus prednisone treatment, and 42 patients were randomized to prednisone treatment. Serum samples were analyzed for the expression of miR-150-5p and miR-21-5p, with quantitative reverse transcriptase PCR at baseline and at 12, 24, and 36 months after randomization. The inclusion criteria for participation in the MGTX trial were age 18-65 years, generalized myasthenia gravis (Myasthenia Gravis Foundation of America Class II-IV), disease duration of less than 5 years, and seropositivity for acetylcholine receptor antibodies (AChR+).

Results

Patients treated with thymectomy had lower levels of miR-150-5p at 24 months, both compared with baseline values (p = 0.0011) and the prednisone group (p = 0.04). No change in miRNA levels was found in the prednisone group. Levels of miR-21-5p displayed a negative correlation with the prednisone dose within the prednisone-only group (p ≤ 0.001).

Conclusions

Thymectomy lowers the levels of the proposed biomarker miR-150-5p, which strengthens its position as a potential disease-specific biomarker for AChR+ MG.

Prognosis of Ocular Myasthenia Gravis in an Argentinian Population

BACKGROUND

We investigated the prognosis of patients with myasthenia gravis (MG) initially presenting with only ocular symptoms in an Argentinian population.

SUMMARY

We performed a retrospective analysis of 61 patients with MG with pure ocular involvement at onset. Generalized MG (gMG) developed in 73.7% of patients, while the rest only exhibited ocular symptoms throughout the course of the disease (ocular MG [oMG]). The AChR antibody (AChR-ab) was found in 81.4% of the gMG and 50% of the oMG cases. AChR-ab titers were also significantly higher in the gMG than in the oMG group. Patients with oMG more frequently required treatment only with acetylcholinesterase inhibitors and showed more remissions. Key Messages: Our study showed high generalization in patients with MG debuting with ocular symptoms. Patients with AChR seropositivity and higher AChR-ab titers had an increased risk for gMG, while patients with oMG showed lower corticosteroid requirements and a higher remission rate.

Thymus imaging in myasthenia gravis: The relevance in clinical practice

INTRODUCTION

The ability to distinguish between normal thymus, thymic hyperplasia, and thymoma should aid clinical management and decision making in patients with myasthenia gravis (MG). We sought to determine the accuracy of routine imaging in predicting thymic pathology.

METHODS

We retrospectively analyzed records of patients with MG from the Oxford Myasthenia Centre registry who had undergone thymectomy. Each patient received 1 radiological diagnosis and 1 histological diagnosis.

RESULTS

We included 106 patients. Radiological and histological diagnoses agreed in 73 (68.9%) patients. Sensitivity and specificity, respectively, were calculated for each radiological diagnosis as follows: thymoma 90% and 95.5%, hyperplasia 17.6% and 98.6%, and normal 96.9% and 60.8%.

DISCUSSION

Routine chest computed tomography and MRI can effectively identify thymoma. However, they are not reliable tools to differentiate between thymic hyperplasia and normal thymus in patients with MG. Muscle Nerve, 2018.

The thymidylate synthase enhancer region (TSER) polymorphism increases the risk of thymic lymphoid hyperplasia in patients with Myasthenia Gravis

BACKGROUND

Myasthenia Gravis (MG) is caused, in approximately 80% of the patients, by autoantibodies against the nicotinic acetylcholine receptor (AChR). The disease is often associated with pathological changes of the thymus: thymic epithelial tumours are present in about 10-20% of the patients, while up to 80% of the patients with early disease onset have thymic hyperplasia. Folate metabolism is required for the production of DNA precursors and for proper DNA methylation reactions, and impaired folate metabolism has been often associated with cellular growth and cancer.

METHODS

We investigated if major polymorphisms of folate-related genes, namely MTHFR c.677C>T, MTR c.2756A>G, MTRR c.66A>G and TYMS TSER (a 28-bp tandem repeat in the 5' promoter enhancer region of TYMS) increase the risk of pathological changes of the thymus in AChR+ MG patients. A total of 526 AChR+ MG patients, including 132 patients with normal (involuted) thymus, 146 patients with thymic hyperplasia, and 248 patients with a thymoma were included in the study. Allele and genotype comparisons were performed among the three study groups, after correcting for multiple testing.

RESULTS

The frequency of the TYMS TSER 3R allele was significantly higher in MG patients with thymic hyperplasia (P=0.004), and the TYMS TSER 3R3R genotype was significantly associated with increased risk of thymic hyperplasia [OR 2.71 (95% CI: 1.34-5.47)].

CONCLUSIONS

The 3R allele in the thymidylate synthase promoter enhancer region results in increased protein production, required for the synthesis of DNA precursors. The present study suggests that the TYMS TSER 3R allele increases the risk of thymic lymphoid hyperplasia in AChR+ MG patients.

Toll-like receptor 9 antagonist suppresses humoral immunity in experimental autoimmune myasthenia gravis

Recent studies have demonstrated the important role of toll-like receptor 9 (TLR9) signalling in autoimmune diseases, but its role in myasthenia gravis (MG) has not been fully established. We show herein that blocking TLR9 signalling via the suppressive oligodeoxynucleotide (ODN) H154 alleviated the symptoms of experimental autoimmune myasthenia gravis (EAMG). With the downregulation of dendritic cells (DCs), TLR9 interruption reduced follicular helper T cells (Tfh) and germinal centre (GC) B cells, leading to decreased antibody production. In addition, TLR9⁺ B cells as well as total B cells in the spleen were inhibited by H154. These findings highlight the critical role of TLR9 in EAMG and suggest that the inhibition of the TLR9 pathway might be a potential pharmacological strategy for the treatment of myasthenia gravis.

Mechanisms underlying B cell immune dysregulation and autoantibody production in MuSK myasthenia gravis

Pathogenic autoantibodies to muscle-specific tyrosine kinase (MuSK) can be found in patients with myasthenia gravis (MG) who do not have detectable antibodies to the acetylcholine receptor. Although the autoantibody-mediated pathology is well understood, much remains to be learned about the cellular immunology that contributes to autoantibody production. To that end, our laboratory has investigated particular components associated with the cellular immunopathology of MuSK MG. First, we found that B cell tolerance defects contribute to the abnormal development of the naive repertoire, which indicates that dysregulation occurs before the production of autoantibodies. Second, both the naive and antigen-experienced memory B cell repertoire, which we examined through the application of high-throughput adaptive immune receptor repertoire sequencing, include abnormalities not found in healthy controls. This highlights a broad immune dysregulation. Third, using complementary approaches, including production of human monoclonal antibodies, we determined that circulating plasmablasts directly contribute to the production of MuSK-specific autoantibodies in patients experiencing relapse following B cell depletion therapy. These collective findings contribute to defining a mechanistic model that describes MuSK MG immunopathogenesis.

Myasthenia gravis with antibodies to MuSK: an update

Myasthenia gravis with antibodies to the muscle-specific tyrosine kinase (MuSK⁺ MG) is a rare disease with distinctive pathogenic mechanisms and clinical features. An acute onset and predominant bulbar muscle weakness are very common and highly suggestive of the disease. On the other hand, a more indolent course, atypical ocular presentation, and signs of cholinergic hyperactivity may complicate the diagnosis. Though MuSK⁺ MG is still a severe disease, over the years we have observed a steady reduction in the rate of respiratory crisis and a significant improvement in the clinical outcome, both likely related to earlier diagnosis and timely treatment. Despite the improved management, MuSK⁺ MG patients tend to remain dependent on long-term immunosuppressive treatment and may develop permanent disabling weakness. In uncontrolled studies, B cell depletion with rituximab proved effective in most patients with refractory disease, inducing prolonged clinical responses associated with a sustained reduction of serum antibody levels. Promising results from experimental studies and case reports suggest that both 3,4-diaminopyridine and albuterol may be effective as symptomatic agents.

Immunopathogenesis in Myasthenia Gravis and Neuromyelitis Optica

Myasthenia gravis (MG) and neuromyelitis optica (NMO) are autoimmune channelopathies of the peripheral neuromuscular junction (NMJ) and central nervous system (CNS) that are mainly mediated by humoral immunity against the acetylcholine receptor (AChR) and aquaporin-4 (AQP4), respectively. The diseases share some common features, including genetic predispositions, environmental factors, the breakdown of tolerance, the collaboration of T cells and B cells, imbalances in T helper 1 (Th1)/Th2/Th17/regulatory T cells, aberrant cytokine and antibody secretion, and complement system activation. However, some aspects of the immune mechanisms are unique. Both targets (AChR and AQP4) are expressed in the periphery and CNS, but MG mainly affects the NMJ in the periphery outside of CNS, whereas NMO preferentially involves the CNS. Inflammatory cells, including B cells and macrophages, often infiltrate the thymus but not the target—muscle in MG, whereas the infiltration of inflammatory cells, mainly polymorphonuclear leukocytes and macrophages, in NMO, is always observed in the target organ—the spinal cord. A review of the common and discrepant characteristics of these two autoimmune channelopathies may expand our understanding of the pathogenic mechanism of both disorders and assist in the development of proper treatments in the future.

Malignant thymoma with metastasis associated with paraneoplastic myasthenia gravis

We describe a patient who initially presented with a mixed thymic tumor and developed myasthenia gravis 8 years following thymectomy with recurrence of metastatic disease. Metastasis to the pleura, mediastinum, and cervical spine was identified with a positron emission tomography scan when this patient presented with recurring pneumonias and atrial fibrillation. The presentation and diagnosis were clouded by multiple courses of prednisone and chemotherapy for respiratory complications and metastatic disease, respectively. Classical myasthenia gravis symptoms emerged when his prednisone was tapered. The delayed presentation of paraneoplastic disease and the rare metastatic site make this case particularly unusual.