Treatment and outcome of myasthenia gravis: retrospective multi-center analysis of 470 Japanese patients, 1999–2000

Short-term outcome prediction for myasthenia gravis: an explainable machine learning model

Background

Myasthenia gravis (MG) is an autoimmune disease characterized by muscle weakness and fatigability. The fluctuating nature of the disease course impedes the clinical management.

Objective

The purpose of the study was to establish and validate a machine learning (ML)-based model for predicting the short-term clinical outcome in MG patients with different antibody types.

Methods

We studied 890 MG patients who had regular follow-ups at 11 tertiary centers in China from 1 January 2015 to 31 July 2021 (653 patients for derivation and 237 for validation). The short-term outcome was the modified post-intervention status (PIS) at a 6-month visit. A two-step variable screening was used to determine the factors for model construction and 14 ML algorithms were used for model optimisation.

Results

The derivation cohort included 653 patients from Huashan hospital [age 44.24 (17.22) years, female 57.6%, generalized MG 73.5%], and the validation cohort included 237 patients from 10 independent centers [age 44.24 (17.22) years, female 55.0%, generalized MG 81.2%]. The ML model identified patients who were improved with an area under the receiver operating characteristic curve (AUC) of 0.91 [0.89-0.93], 'Unchanged' 0.89 [0.87-0.91], and 'Worse' 0.89 [0.85-0.92] in the derivation cohort, whereas identified patients who were improved with an AUC of 0.84 [0.79-0.89], 'Unchanged' 0.74 [0.67-0.82], and 'Worse' 0.79 [0.70-0.88] in the validation cohort. Both datasets presented a good calibration ability by fitting the expectation slopes. The model is finally explained by 25 simple predictors and transferred to a feasible web tool for an initial assessment.

Conclusion

The explainable, ML-based predictive model can aid in forecasting the short-term outcome for MG with good accuracy in clinical practice.

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

INTRODUCTION

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

PATIENTS AND METHODS

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

RESULTS

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

CONCLUSION

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

Thymectomy and Risk of Generalization in Patients with Ocular Myasthenia Gravis: A Multicenter Retrospective Cohort Study

This study aims to investigate the association between thymectomy and the risk of generalization in patients with ocular myasthenia gravis (MG). Data on patients with ocular MG from seven neurological centers in China were retrospectively reviewed. Ocular MG naïve to immunotherapy was categorized according to whether thymectomy was performed (thymectomized group vs. nonsurgical group). Patients in the thymectomized group all underwent surgery within 2 years since ocular symptom onset. The main outcome measure was the generalization. The follow-up period was defined from the date of ocular symptom onset to the date of generalization confirmation, immunotherapy initiation, or last follow-up (defined as 60 months). Of 519 eligible patients (mean [SD] age, 48.7 [15.2] years, 46.6% women), 31 (23.7%) of 131 generalized in the thymectomized group and 122 (31.4%) of 388 did in the nonsurgical group during a median follow-up of 19 months (IQR 8.0-50.0). Thymectomy was independently associated with reduced generalization risk (adjusted HR 0.41, 95% CI 0.25-0.66, P < 0.001). Multivariable stratified analysis also verified this association across the subgroups. Kaplan-Meier curves showed that the 5-year cumulative rate was significantly lower in the thymectomized group than in the nonsurgical group. To conclude, thymectomy may be considered effective in modifying the progression from ocular to generalized MG irrespective of thymoma.

Pediatric Ocular Myasthenia Gravis: A Review

Pediatric ocular myasthenia gravis (OMG) is difficult to diagnose and manage, owing to its rarity and low index of suspicion in the early stage of the disease. Also, many other conditions having similar presentation cause a further delay in diagnosis. In this review, we highlighted various pointers in history and described bedside clinical tests that can aid in its timely diagnosis. The antibody spectrum in myasthenia is ever increasing and includes anti-muscle specific kinase and low-density lipoprotein-receptor related protein 4 antibodies in addition to acetylcholine receptor antibodies besides many others. However, pediatric OMG patients often test negative for all three antibodies, making the diagnosis even more difficult in triple seronegative patients. Edrophonium and electrophysiological tests, which help in confirming myasthenia in adults, have a limited utility in diagnosing pediatric ocular myasthenia cases. Various practical difficulties are encountered like nonavailability of edrophonium, risk of bradycardia associated with neostigmine use and its lower sensitivity, noncooperative children, and limited technical expertise in performing electrophysiological tests in children. In this article, we described a pragmatic approach to diagnose pediatric OMG along with the important aspects of its management.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Reappraisal of Oral Steroid Therapy for Myasthenia Gravis

Treatment with oral corticosteroids at high doses with an escalation and de-escalation schedule is effective against myasthena gravis (MG). In fact, the use of corticosteroids has led to a reduction in mortality to below 10% after the 1960s. However, long-term use of oral steroids above a certain dosage level is known to cause a number of problems. In 2014, the Japanese clinical guidelines for MG proposed that the first goal in MG treatment (treatment target) should be set at minimal manifestations (MM) with oral prednisolone (PSL) 5 mg/day or below, and that treatment strategies should strive to attain this level as rapidly as possible. In 2015, a multicenter, cross-sectional study revealed that higher PSL dose and longer PSL treatment do not ensure better outcome. In the absence of good response, the PSL dose should be decreased by combining with modalities such as plasma exchange/plasmapheresis and intravenous immunoglobulin (fast-acting treatments). In 2018, we conducted a multicenter, cross-sectional study in a large population of Japanese patients with generalized MG, aiming to elucidate the correlation between oral PSL regimens and achievement of treatment goals. The ORs for low vs. high dose to achieve treatment goals at 1, 2, and 3 years were 10.4, 2.75, and 1.86, respectively, whereas the corresponding ORs for low vs. medium dose were 13.4, 3.99, and 4.92. Early combination with fast-acting therapy (OR 2.19 at 2 years, 2.11 at 3 years) or combination with calcineurin inhibitors (OR 2.09 at 2 years, 2.36 at 3 years) were also positively associated with achieving treatment goals. These results indicate that early combination of low-dose PSL regimens with other therapies is the key for early achievement of treatment goals in generalized MG. However, even with this regimen, ~35% of patients did not achieve the treatment target after 3 years. These results suggest the limitation of the current oral corticosteroid therapy. We need to develop new treatment options to increase the rate of satisfactory outcome.

Minimal manifestation status and prednisone withdrawal in the MGTX trial

OBJECTIVE

To examine whether sustained minimal manifestation status (MMS) with complete withdrawal of prednisone is better achieved in thymectomized patients with myasthenia gravis (MG).

METHODS

This study is a post hoc analysis of data from a randomized trial of thymectomy in MG (Thymectomy Trial in Non-Thymomatous Myasthenia Gravis Patients Receiving Prednisone Therapy [MGTX]). MGTX was a multicenter, randomized, rater-blinded 3-year trial that was followed by a voluntary 2-year extension for patients with acetylcholine receptor (AChR) antibody-positive MG without thymoma. Patients were randomized 1:1 to thymectomy plus prednisone vs prednisone alone. Participants were age 18-65 years at enrollment with disease duration less than 5 years. All patients received oral prednisone titrated up to 100 mg on alternate days until they achieved MMS, which prompted a standardized prednisone taper as long as MMS was maintained. The achievement rate of sustained MMS (no symptoms of MG for 6 months) with complete withdrawal of prednisone was compared between the thymectomy plus prednisone and prednisone alone groups.

RESULTS

Patients with MG in the thymectomy plus prednisone group achieved sustained MMS with complete withdrawal of prednisone more frequently (64% vs 38%) and quickly compared to the prednisone alone group (median time 30 months vs no median time achieved, p < 0.001) over the 5-year study period. Prednisone-associated adverse symptoms were more frequent in the prednisone alone group and distress level increased with higher doses of prednisone.

CONCLUSIONS

Thymectomy benefits patients with MG by increasing the likelihood of achieving sustained MMS with complete withdrawal of prednisone.

CLINICALTRIALSGOV IDENTIFIER

NCT00294658.

CLASSIFICATION OF EVIDENCE

This study provides Class II evidence that for patients with generalized MG with AChR antibody, those receiving thymectomy plus prednisone are more likely to attain sustained MMS and complete prednisone withdrawal than those on prednisone alone.

Update on immune-mediated therapies for myasthenia gravis

With the exception of thymectomy, immune modulatory treatment strategies and clinical trials in myasthenia gravis over the past 50 y were mainly borrowed from experience in other nonneurologic autoimmune disorders. The current experimental therapy paradigm has significantly changed such that treatments directed against the pathological mechanisms specific to myasthenia gravis are being tested, in some cases as the initial disease indication. Key advances have been made in three areas: (i) the expanded role and long-term benefits of thymectomy, (ii) complement inhibition to prevent antibody-mediated postsynaptic membrane damage, and (iii) neonatal Fc receptor (FcRn) inhibition as in vivo apheresis, removing pathogenic antibodies. Herein, we discuss these advances and the potential for these newer therapies to significantly influence the current treatment paradigms. While these therapies provide exciting new options with rapid efficacy, there are anticipated challenges to their use, especially in terms of a dramatic increase in cost of care for some patients with myasthenia gravis.

Long-term efficacy and safety of eculizumab in Japanese patients with generalized myasthenia gravis: A subgroup analysis of the REGAIN open-label extension study

The terminal complement inhibitor eculizumab was shown to improve myasthenia gravis-related symptoms in the 26-week, phase 3, randomized, double-blind, placebo-controlled REGAIN study (NCT01997229). In this 52-week sub-analysis of the open-label extension of REGAIN (NCT02301624), eculizumab's efficacy and safety were assessed in 11 Japanese and 88 Caucasian patients with anti-acetylcholine receptor antibody-positive refractory generalized myasthenia gravis. For patients who had received placebo during REGAIN, treatment with open-label eculizumab resulted in generally similar outcomes in the Japanese and Caucasian populations. Rapid improvements were maintained for 52 weeks, assessed by change in score from open-label extension baseline to week 52 (mean [standard error]) using the following scales (in Japanese and Caucasian patients, respectively): Myasthenia Gravis Activities of Daily Living (-2.4 [1.34] and - 3.3 [0.65]); Quantitative Myasthenia Gravis (-2.9 [1.98] and - 4.3 [0.79]); Myasthenia Gravis Composite (-4.5 [2.63] and - 4.9 [1.19]); and Myasthenia Gravis Quality of Life 15-item questionnaire (-8.6 [5.68] and - 6.5 [1.93]). Overall, the safety of eculizumab was consistent with its known safety profile. In this interim sub-analysis, the efficacy and safety of eculizumab in Japanese and Caucasian patients were generally similar, and consistent with the overall REGAIN population.

Long-term effect of thymectomy plus prednisone versus prednisone alone in patients with non-thymomatous myasthenia gravis: 2-year extension of the MGTX randomised trial

BACKGROUND

The Thymectomy Trial in Non-Thymomatous Myasthenia Gravis Patients Receiving Prednisone (MGTX) showed that thymectomy combined with prednisone was superior to prednisone alone in improving clinical status as measured by the Quantitative Myasthenia Gravis (QMG) score in patients with generalised non-thymomatous myasthenia gravis at 3 years. We investigated the long-term effects of thymectomy up to 5 years on clinical status, medication requirements, and adverse events.

METHODS

We did a rater-blinded 2-year extension study at 36 centres in 15 countries for all patients who completed the randomised controlled MGTX and were willing to participate. MGTX patients were aged 18 to 65 years at enrolment, had generalised non-thymomatous myasthenia gravis of less than 5 years' duration, had acetylcholine receptor antibody titres of 1·00 nmol/L or higher (or concentrations of 0·50-0·99 nmol/L if diagnosis was confirmed by positive edrophonium or abnormal repetitive nerve stimulation, or abnormal single fibre electromyography), had Myasthenia Gravis Foundation of America Clinical Classification Class II-IV disease, and were on optimal anticholinesterase therapy with or without oral corticosteroids. In MGTX, patients were randomly assigned (1:1) to either thymectomy plus prednisone or prednisone alone. All patients in both groups received oral prednisone at doses titrated up to 100 mg on alternate days until they achieved minimal manifestation status. The primary endpoints of the extension phase were the time-weighted means of the QMG score and alternate-day prednisone dose from month 0 to month 60. Analyses were by intention to treat. The trial is registered with ClinicalTrials.gov, number NCT00294658. It is closed to new participants, with follow-up completed.

FINDINGS

Of the 111 patients who completed the 3-year MGTX, 68 (61%) entered the extension study between Sept 1, 2009, and Aug 26, 2015 (33 in the prednisone alone group and 35 in the prednisone plus thymectomy group). 50 (74%) patients completed the 60-month assessment, 24 in the prednisone alone group and 26 in the prednisone plus thymectomy group. At 5 years, patients in the thymectomy plus prednisone group had significantly lower time-weighted mean QMG scores (5·47 [SD 3·87] vs 9·34 [5·08]; p=0·0007) and mean alternate-day prednisone doses (24 mg [SD 21] vs 48 mg [29]; p=0·0002) than did those in the prednisone alone group. 14 (42%) of 33 patients in the prednisone group, and 12 (34%) of 35 in the thymectomy plus prednisone group, had at least one adverse event by month 60. No treatment-related deaths were reported during the extension phase.

INTERPRETATION

At 5 years, thymectomy plus prednisone continues to confer benefits in patients with generalised non-thymomatous myasthenia gravis compared with prednisone alone. Although caution is appropriate when generalising our findings because of the small sample size of our study, they nevertheless provide further support for the benefits of thymectomy in patients with generalised non-thymomatous myasthenia gravis.

FUNDING

National Institutes of Health, National Institute of Neurological Disorders and Stroke.

Thymectomy is a beneficial therapy for patients with non-thymomatous ocular myasthenia gravis: a systematic review and meta-analysis

Ocular myasthenia gravis, an autoimmune disease, is characterized by extraocular muscle weakness. Myasthenia gravis is closely associated with the functional status of the thymus gland. The efficacy of thymectomy for non-thymomatous ocular myasthenia gravis remains controversial. Here, we present the first systematic review and meta-analysis of studies assessing the outcome of thymectomy in patients with non-thymomatous ocular myasthenia gravis and found that the pooled rate of complete stable remission was 0.5074 with considerable heterogeneity. Furthermore, subgroup analysis showed that the efficacy of thymectomy differed according to geographical location. Furthermore, thymectomy outcomes are better in children than they are in adults. Thymectomy clearly represents an effective treatment for patients with non-thymomatous ocular myasthenia gravis. However, more multicenter, randomized, controlled clinical trials are now required to confirm these conclusions.

Factors predicting the outcomes of elderly hospitalized myasthenia gravis patients: a national database study

Background

Myasthenia gravis (MG) in elderly populations is increasing. This study aimed to evaluate predictors for treatment outcomes in elderly hospitalized MG patients using the national database.

Methods

We collected data of elderly hospitalized MG patients from the National Health Security Office from October 2009 to September 2010. Predictors for treatment outcomes were examined.

Results

During the study period, 1,948 identified MG patients were admitted to hospitals throughout Thailand. Of those, 441 patients (22.64%) were aged ≥ 60 years. There were 66 patients (14.97%) who had poor outcomes. There were only three significant factors in the final model. Presence of pneumonia, use of mechanical ventilators, and septicemia had adjusted odds ratios (95% confidence interval) of 2.83 (1.03, 7.75), 5.33 (2.24, 12.72), and 4.47 (1.86, 10.75), respectively.

Conclusion

Pneumonia, being on a mechanical ventilator, and septicemia were independent factors associated with poor treatment outcomes in elderly hospitalized MG patients according to national data.

Low-Dose Medication and Long-Term Outcome in Myasthenia Gravis

OBJECTIVES

Many advances have been made in the diagnosis, treatment, and management of myasthenia gravis (MG) and most patients will eventually progress to experience minimal manifestations (MM) of the disease or remission. However, there is a paucity of literature on medication dosing needed to achieve such a favorable clinical status in the long term. The objective of this article was to (1) study the course of MG and identify clinical predictors of maintenance of eventual disease remission or minimal manifestations and (2) determine if patients on low-dose medications have comparable MG Foundation of America (MGFA) scores and postintervention statuses (PIS) with those on conventional therapeutic dosing.

METHODS

This is a retrospective longitudinal chart review of 74 patients with MG. A subset of 28 of 74 patients diagnosed with MG after 2000 who were followed for at least 3 consecutive years from the year of diagnosis were also analyzed. An annual MGFA score, PIS, medication doses, and thymectomy status were obtained. Remission or MM of disease was defined as MGFA clinical classification <2 that persisted over the past 2 follow-up visits.

RESULTS

Thirty-four of 74 patients were on low-dose medications at last follow-up. There was no statistical difference between medication dosages and MGFA scores. In a subset of 28 patients, 23 (88.5%) with eventual disease remission or MM at last follow-up had an MGFA class <2 at their third year of diagnosis. In contrast, only 3 of 9 subjects with more symptomatic disease had similar results (P = 0.005). In terms of PIS at last follow-up, most patients were either in complete stable remission, pharmacologic remission, or MM status. Most patients (78.3%) had an MGFA class of 0 or 1 at last follow-up; 45% were on low-dose medications.

CONCLUSIONS

Most patients with MG will realize disease stability characterized by either remission or MM status. A significant number of such patients were able to be maintained on low doses of medications to treat MG. The MGFA class at year 3 of diagnosis is a clinical predictor of long-term disease prognosis. There was no statistical difference between medication doses and MGFA scores at last follow-up.

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.

CTLA4 variants and haplotype contribute genetic susceptibility to myasthenia gravis in northern Chinese population

BACKGROUND

Cytotoxic T lymphocyte-associated antigen-4 (CTLA4), a critical negative regulator of the T-cell response, has been considered a candidate for many autoimmune diseases. Evidence from Caucasians supported a genetic predisposition of CTLA4 to myasthenia gravis (MG), but the contribution in East Asians has not been established.

OBJECTIVES

To investigate the role of CTLA4 variants in the susceptibility to MG and the contribution to subtypes of MG.

METHODS

Six autoimmune disease-related risk alleles of CTLA4 (rs1863800, rs733618, rs4553808, rs5742909, rs231775, and rs3087243) were investigated for MG in northern Chinese. 168 patients with MG (mean age 37.1±20.5 years, 64 men and 104 women) and 233 healthy controls (mean age 53.3±8.7 years, 96 men and 137 women) were screened, and the contribution of CTLA4 to the general risk of MG and each subgroup was explored.

RESULTS

rs1863800*C, rs733618*C, and rs231775*G were significantly associated with the whole cohort of patients with MG after permutation correction for multiple-testing adjustment (P = 0.027, 0.001, and 0.032, respectively). A risk haplotype (CCACG) [odds ratio (OR) = 1.535, range = 1.150-2.059, P = 0.004)] was also identified. The stratified subtype analysis indicated that the positive contribution was possibly derived from early onset MG (EOMG), seropositive MG (SPMG), female patients, and MG without thymoma. No association was observed in juvenile MG/LOMG, and MG coupled with thymoma.

CONCLUSION

A predisposing effect of rs1863800*C, rs733618*C, and rs231775*G of CTLA4 gene to general risk of MG in Chinese was demonstrated for the first time, which was likely derived from EOMG, SPMG, MG without thymoma and the female patients.

Treatment-refractory myasthenia gravis

Myasthenia gravis (MG) is the most common disorder of neuromuscular transmission and is a prototypical autoimmune disorder. Most patients with MG are successfully treated with acetylcholinesterase inhibitors, corticosteroids, and/or steroid sparing agents such as azathioprine and mycophenolate mofetil. There is a small subset of patients, however, with treatment-refractory disease. In these cases, medications such as rituximab, high-dose cyclophosphamide, and eculizumab may be used. Thymectomy (in some cases repeat thymectomy) is another option in selected patients. Studies evaluating these and other forms of therapy in treatment-refractory MG are reviewed.

Muscle strength in myasthenia gravis

OBJECTIVE

Myasthenia gravis (MG) is characterized by fatigue and fluctuating muscle weakness as a result of impaired neuromuscular transmission (NMT). Although MG is a prototypic fatiguing disorder, little is known about how the condition affects fixed weakness, and if present, whether weakness is related to disease duration or gender. The aim of this study was to quantify the strength of patients with MG and investigate whether it is related to disease duration.

METHODS

Eight muscle groups were tested by manual muscle testing and with a hand-held dynamometer in 38 patients with generalized MG and 37 healthy age- and gender-matched controls. The disease duration was recorded and compared with strength measures.

RESULTS

On average, muscle strength was decreased by 28% compared with controls (P<0.01). Repeated strength measures in individual patients did not differ, suggesting that the muscle force reported was not subject to fatigue, but reflected fixed weakness. The male patients showed a greater reduction in muscle force in all eight muscle groups than women with MG (60% vs 77% of normal, P<0.05). In both men and women with MG, strength in shoulder abductors was most affected (51% vs 62% of normal). Muscle strength and disease duration were not related.

CONCLUSIONS

These findings show that patients with generalized MG have (i) a significant generalized, fixed muscle weakness, (ii) that male patients with MG have a more severe muscle weakness than women, (iii) that proximal upper limb muscles are most affected, and (iv) that disease duration alone is not a predictor of loss of muscle strength.

EFNS/ENS Guidelines for the treatment of ocular myasthenia

BACKGROUND AND PURPOSE

The symptoms of acquired autoimmune ocular myasthenia are restricted to the extrinsic eye muscles, causing double vision and drooping eyelids. These guidelines are designed to provide advice about best clinical practice based on the current state of clinical and scientific knowledge and the consensus of an expert panel.

SEARCH STRATEGY

Evidence for these guidelines was collected by searches in the MEDLINE and Cochrane databases. The task force working group reviewed evidence from original articles and systematic reviews. The evidence was classified (I, II, III, IV) and consensus recommendation graded (A, B or C) according to the EFNS guidance. Where there was a lack of evidence but clear consensus, good practice points are provided.

CONCLUSIONS

The treatment of ocular myasthenia should initially be started with pyridostigmine (good practice point). If this is not successful in relieving symptoms, oral corticosteroids should be used on an alternate-day regimen (recommendation level C). If steroid treatment does not result in good control of the symptoms or if it is necessary to use high steroid doses, steroid-sparing treatment with azathioprine should be started (recommendation level C). If ocular myasthenia gravis is associated with thymoma, thymectomy is indicated. Otherwise, the role of thymectomy in ocular myasthenia is controversial. Steroids and thymectomy may modify the course of ocular myasthenia and prevent myasthenia gravis generalization (good practice point).

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.

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.

Medical and surgical treatment for ocular myasthenia

BACKGROUND

Approximately 50% of people with myasthenia gravis present with purely ocular symptoms, so called ocular myasthenia. Of these between 50% to 60% develop generalized disease, most within two years. Their management is controversial. This is an update of a review first published in 2006 and previously updated in 2008 and 2010.

OBJECTIVES

To assess the effects of treatments for ocular myasthenia and to answer three specific questions. Are there any treatments that impact the progression from ocular to generalized disease? Are there any treatments that improve symptoms of diplopia or ptosis? What is the frequency of adverse effects associated with treatments used?

SEARCH METHODS

In this updated review, we searched the Cochrane Neuromuscular Disease Group Specialized Register (3 August 2012), CENTRAL (2012, Issue 7), MEDLINE (January 1996 to July 2012) and EMBASE (January 1974 to July 2012) for randomized controlled trials (RCTs) as well as case-control and cohort studies. The titles and abstracts of all articles were read by both authors and the full texts of possibly relevant articles were reviewed. The references of all manuscripts included in the review were scanned to identify additional articles of relevance and experts in the field were contacted to identify additional published and unpublished data. Where necessary, we contacted authors for further information.

SELECTION CRITERIA

Inclusion required meeting three criteria: (a) randomized (or quasi-randomized) controlled study design; (b) active treatment compared to placebo, no treatment or some other treatment; and (c) results reported separately for patients with ocular myasthenia (grade 1) as defined by the Myasthenia Gravis Foundation of America.

DATA COLLECTION AND ANALYSIS

We collected data regarding the risk of progression to generalized myasthenia gravis, improvement in ocular symptoms, and the frequency of treatment-related side effects.

MAIN RESULTS

In the original review, we identified two RCTs relevant to the treatment of ocular myasthenia, only one of which reported results in terms of the pre-specified outcome measures used in this review. This study included only three participants and was of limited methodological quality. There were no new RCTs in searches conducted for this or previous updates. In the absence of data from RCTs, we present a review of the available observational data.

AUTHORS' CONCLUSIONS

The available randomized controlled literature does not permit any meaningful conclusions about the efficacy of any form of treatment for ocular myasthenia. Data from several reasonably good quality observational studies suggest that corticosteroids and azathioprine may be beneficial in reducing the risk of progression to generalized myasthenia gravis.

Complete Remission of Generalized Myasthenia Gravis by Corticosteroid Treatment Alone without Thymectomy

Many long-term, follow-up studies have shown that steroids are effective in patients with myasthenia gravis (MG) who have undergone thymectomy. However, few long-term studies have documented the response of MG to steroids alone. We describe two patients who successfully resolved the symptoms of MG without myasthenic crisis or serious side effects by steroid treatment without thymectomy or other alternative therapies for more than 19 years. Our experiences raise an open question of the role of thymectomy or steroid treatment alone, especially in MG patients without thymoma.

Juvenile myasthenia gravis: a paediatric perspective

Myasthenia gravis (MG) is an autoimmune disease in which antibodies are directed against the postsynaptic membrane of the neuromuscular junction, resulting in muscle weakness and fatigability. Juvenile myasthenia gravis (JMG) is a rare condition of childhood and has many clinical features that are distinct from adult MG. Prepubertal children in particular have a higher prevalence of isolated ocular symptoms, lower frequency of acetylcholine receptor antibodies, and a higher probability of achieving remission. Diagnosis in young children can be complicated by the need to differentiate from congenital myasthenic syndromes, which do not have an autoimmune basis. Treatment commonly includes anticholinesterases, corticosteroids with or without steroid-sparing agents, and newer immune modulating agents. Plasma exchange and intravenous immunoglobulin (IVIG) are effective in preparation for surgery and in treatment of myasthenic crisis. Thymectomy increases remission rates. Diagnosis and management of children with JMG should take account of their developmental needs, natural history of the condition, and side-effect profiles of treatment options.

[Standard treatment for late-onset myasthenia gravis in Japan]

Myasthenia gravis (MG) is caused by the failure of neuromuscular transmission mediated by autoantibodies against acetylcholine receptors (AChR) and muscle-specific receptor tyrosine kinase (MuSK). These seropositivity rates in AChR positive and MuSK positive MG in Japan are 80-85% and 5-10%, respectively. The incidence of late-onset MG has been increasing all over the world. A nationwide epidemiological survey in Japan also revealed that the rates of late-onset MG (onset after 50 years) had increased from 20% in 1987 to 42% in 2006. In 2010, a guideline for standard treatments in late-onset MG was published from Japanese Scoiety of Neurological Therapeutics. Based on individual experiences and the limited evidence, epidemiological characteristics of MG onset age, clinical features, and the standard treatment for late-onset patients are included in it. In this guideline summary, the ocular form was more frequent in late-onset compared to early-onset group, the indication of thymectomy in late-onset MG is less than that of early-onset MG and the combination of corticosteroids and immunosuppressive agents are recommended in order to reduce doses of corticosteroids in late-onset MG.

Pharmacologic agents for pediatric neuroimmune disorders

Autoimmune diseases make up a significant portion of the acute and chronic caseload of all pediatric neurologists. By comparing these diseases and their treatments side by side, common themes become evident. Therapeutic decisions follow patterns dependent on the clinical situation. Physicians must adapt therapy based on individual clinical responses. This article provides an overview of the current therapeutic options as they relate to the more common pediatric neuroimmune disorders.

Factors associated with response to calcineurin inhibitors in myasthenia gravis

The objective was to assess which clinical factors of patients with myasthenia gravis (MG) are associated with responsiveness to calcineurin inhibitors (CNIs, cyclosporine and tacrolimus). We retrospectively analyzed the 6-month effects of CNIs in 62 MG patients. We excluded the influence of other immune treatments and determined factors associated with response to CNIs. The frequency of patients who achieved neither a > or =3-point reduction in quantitative MG score nor a > or =25% reduction in daily dose of prednisolone (poor responders) reached 35.5% (22/62) and 64.5% (40/62), respectively, compared with patients who achieved at least one of these improvements (responders). Neither dose nor blood concentration of CNIs differed between groups. Multivariate logistic regression analysis revealed time since onset of disease [odds ratio (OR) = 0.85, P = 0.005] and presence of thymoma (OR = 5.56, P = 0.05) as clinical factors that predict response to CNIs. As for MG-related autoantibody status, an autoantibody against a voltage-gated potassium channel, Kv1.4, was associated with response (OR = 9.01, P = 0.04) and showed a correlation with the presence of thymoma (P < 0.01). In MG, the early stages of disease and thymoma-associated MG are responsive to treatment with CNIs.

Response to therapy in myasthenia gravis with anti-MuSK antibodies

Myasthenia gravis (MG) with antibodies against the muscle-specific tyrosine kinase (MuSK abs) is often a severe disease requiring aggressive treatment. Various immunosuppressive (IS) regimens have been employed; the efficacy of plasma exchange is unanimously recognized, while the indication for thymectomy is controversial. We evaluated the response to therapy in 57 MuSK-positive patients (12 M/45 F) comparing our experience with other authors' results. Disease severity and response to treatment were graded according to MG Foundation of America; follow-up ranged from 0.5-29 years. Owing to both MG severity and the unsatisfactory response to cholinesterase inhibitors, most patients (54/57) needed IS treatment, and 35 received one or more courses of plasma exchange and intravenous immunoglobulin. At the end of follow-up, the rate of complete remission was 8.8%, and IS treatment had been withdrawn in only 10/54 patients. The extent of therapeutic response varied considerably. With conventional IS therapy (prednisone alone or in combination with azathioprine or cyclosporine), most patients achieved good control of their disease, but 30% of them were left with permanent facial and bulbar weakness. In patients with refractory disease, the use of mycophenolate mofetil and rituximab proved very effective, as also reported by other authors. In our and others' experience, MuSK-positive MG markedly improves with IS therapy, although, in comparison with the AChR-positive disease, it is characterized by a lower remission rate, as a higher proportion of patients remain dependent on treatment. Thymectomy is mostly considered scarcely effective; however, at present, no firm conclusions can be drawn on its role in the treatment of this form of MG.

Myasthenia gravis: presentation and outcome in 104 patients managed in a single institution

BACKGROUND AND OBJECTIVES

Few studies have attempted to delineate the clinical profile of myasthenia gravis (MG) among people of Arab ancestry. Therefore, we sought to clarify the clinical profile, the outcome of treatment and the role of thymectomy in non-thymomatous MG in Saudi Arabia.

PATIENTS AND METHODS

We retrospectively studied 104 patients followed over a mean period of 7.2 years (range, 1 to 22 years) at the King Khaled University Hospital, Riyadh, Saudi Arabia. Disease outcomes were compared among thymectomized and non-thymectomized patients according to the post-intervention status criteria of the Myasthenia Gravis Foundation of America (MGFA).

RESULTS

Age of onset was 22.5+/-9.3 years (meanA+/-SD) in females and 28.2+/-15.9 years in males, with peaks in the second and third decades among females and the third and fourth decades among males. At diagnosis, a majority of patients had moderate generalized weakness, equivalent to MGFA class III severity. After medical treatment with or without thymectomy, 9.6% of all patients had achieved complete stable remission, 3.8% had pharmacological remission, 27.9% had minimal manifestations, 23.1% were improved, 20.2% were unchanged and 15.4% were worse. Only thymectomized patients without a thymoma achieved remission, a significant benefit over those who had no thymectomy (P=.02).

CONCLUSION

MG presents at a younger age among Saudi Arabs compared to other racial groups. Thymectomy conferred significant benefits towards achievement of remission.

Myasthenia gravis in South Africans: Racial differences in clinical manifestations

We present data on the phenotypic variation in myasthenia gravis of 205 subjects from a multi-racial South African cohort. Consecutive subjects seen more than twice from 1996 to 2006, were included. Documented observational data included a myasthenia gravis and extra-ocular eye muscle score. Results showed Black subjects were more likely than Whites to develop treatment-resistant complete ophthalmoplegia and ptosis (18% vs. 2%; p=0.041). Of the 14 patients with this phenotype, 13 had generalised disease and positive AChR antibodies. Despite similar sized cohorts, White subjects were more likely than Blacks to develop generalised myasthenia poorly responsive to therapy (p=0.005). There were no significant racial differences in the time between diagnosis to initiation of therapy, or the performance and timing of thymectomy. The racial variation in some phenotypic features of myasthenia gravis and outcome to therapy, highlights the need to study biological factors in different subgroups to develop a more rational approach to immuno-suppressive therapy.

Effects of thymectomy on late-onset myasthenia gravis without thymoma

OBJECTIVES

This study aims to investigate whether thymectomy is beneficial for late-onset (>50 years) myasthenia gravis patients with no thymoma, particularly for those with mild generalized weakness.

PATIENTS AND METHODS

A total of 34 patients were included in the study. The clinical course and long-term outcomes over 2 years were reviewed in 20 patients who underwent thymectomy and in 14 without thymectomy.

RESULTS

Of the 34 patients, 20 (59%) underwent thymectomy. Thymectomized patients had more severe disability at entry than non-thymectomized patients, but outcome measures did not significantly differ between the two patient groups. Moreover, subgroup analyses including 22 patients with mild generalized weakness at entry showed that the thymectomized group (n=10) showed a greater percentage of clinical remission (no symptoms; 50% versus 17%; p=0.11) and a lower frequency of the presence of generalized symptoms (30% versus 75%; p<0.05) than the non-thymectomized group (n=12) at the end of follow-up (means 9.6 years after onset).

CONCLUSIONS

Thymectomy is a potentially effective treatment for late onset, non-thymomatous patients with mild generalized myasthenia gravis.

Clinical features of patients with myasthenia gravis associated with autoimmune diseases

We investigated the incidence and clinical features of patients with myasthenia gravis (MG) associated with autoimmune diseases. Associated autoimmune diseases were found in 28 of 142 consecutive Japanese MG patients (19.7%), amongst which Graves' disease (7.7%) and Hashimoto's thyroiditis (4.2%) were predominant. The clinical features of MG patients with Graves' disease were different from those of MG patients without autoimmune diseases in terms of age at onset of MG symptoms (35.5 +/- 4.0 years and 49.0 +/- 1.7 years; P < 0.05), positivity for the anti-acetylcholine receptor antibody (44.4% and 89.8%; P < 0.05), and association with thymic hyperplasia (72.7 and 17.9%; P < 0.05). The therapeutic outcome of MG patients with Graves' disease and that of those without autoimmune diseases were not significantly different. Further studies should be performed to investigate whether MG associated with Graves' disease is a distinct subtype of MG.

Myasthenic crisis: guidelines for prevention and treatment

Management of myasthenic crisis (MC) requires admission of the patient into a neurological intensive care unit and timely institution of an efficient and safe treatment. Despite the growing clinical experience with disease modifying immunotherapy there is no clinical consensus regarding the use of plasma exchange or high dose immunoglobulin treatment in an ICU setting. The choice of treatment modalities seem to rely mostly on institutional preferences primarily due to a lack of well-designed clinical trials comparing currently available therapeutic options. In our experience and based on a review of recent literature we advocate the use of plasma exchange (PE) as a primary modality in the acute care setting, supported by other immunomodulatory medications such as corticosteroids. Pharmacological management cannot substitute for adequate intensive care management of the respiratory and bulbar insufficiency associated with MC. Every effort should be done to prevent myasthenic exacerbation/crisis and to develop a maintenance management that leads to effective prevention.

Clinical and serological study of myasthenia gravis in HuBei Province, China

BACKGROUND

Ocular and childhood myasthenia gravis (MG) cases seem relatively more common in Oriental than in Caucasian populations, but there have been no comprehensive serological studies on patients from mainland China.

METHODS

391 unselected patients with MG attending Tongji Hospital in WuHan (the largest hospital in the province of HuBei, China) were studied during a 15-month period; most had already received treatment for their condition.

RESULTS

The male to female ratio was 0.8. 50% of the patients were children (<15 years), and age at onset showed a single peak at between 5 and 10 years of age. 64% of the children and 66% of the adults were positive for acetylcholine receptor (AChR) antibodies but the antibody titres were lower than in similar Caucasian studies, although this was partly due to the high incidence of ocular MG. Of the 43 patients with generalised MG without AChR antibodies, only 1 had muscle-specific kinase antibodies (2.5%) and 2 had voltage-gated calcium channel antibodies indicating probable Lambert-Eaton myasthenic syndrome. 75% of the children, compared with only 28% of the adults, had ocular MG. Thymoma was evident by MRI in 1.5% of children and in 20% of adults. Despite most patients having received prednisone, very few had obtained full clinical remission.

CONCLUSION

This study emphasises the frequency of early childhood onset with ocular symptoms and shows that many of these patients have AChR antibodies. By contrast, patients presenting in later age seem to be very uncommon in comparison with recent studies in Caucasian populations.

Medical and surgical treatment for ocular myasthenia

BACKGROUND

Approximately 50% of people with myasthenia gravis present initially with purely ocular symptoms, so called ocular myasthenia and between 50 to 60% of these people will progress to develop generalized disease. The vast majority will do so within the first one to two years. There is controversy surrounding the appropriate management of patients with ocular myasthenia.

OBJECTIVES

To perform a systematic review of the literature relevant to the treatment of ocular myasthenia and to answer three specific questions. Are there any medical or surgical treatments that have an impact on the risk of progression from ocular to generalized myasthenia gravis? Are there any medical or surgical treatments that improve symptoms of diplopia or ptosis in ocular myasthenia? What is the frequency of side effects associated with treatments used in people with ocular myasthenia?

SEARCH STRATEGY

We searched the Cochrane Neuromuscular Disease Group Trials Register (searched December 2004), MEDLINE (1996 to 2004) and EMBASE (1980 to 2004) for randomized controlled trials as well as case-control and cohort studies. The titles and abstracts of all articles were read by both authors and the full text of all articles that were of possible relevance was reviewed in full. The references of all manuscripts included in the review were scanned to identify additional articles of relevance and experts in the field were contacted to identify additional published and unpublished data. Where necessary and possible, we contacted authors for further information.

SELECTION CRITERIA

To be included in the review, studies had to meet three criteria: (a) randomized (or quasi-randomized) controlled study design; (b) active treatment compared to placebo, no treatment or some other treatment; and (c) results reported separately for patients with ocular myasthenia (grade 1) as defined by the Myasthenia Gravis Foundation of America.

DATA COLLECTION AND ANALYSIS

We collected data regarding the risk of progression to generalized myasthenia gravis, improvement in ocular symptoms, and the frequency of treatment-related side effects.

MAIN RESULTS

We identified two randomized controlled trials relevant to the treatment of ocular myasthenia, only one of which reported results in terms of the pre-specified outcome measures used in this review. This study included only three participants and was of limited methodological quality. In the absence of data from randomized controlled trials, we present a review of the available observational data.

AUTHORS' CONCLUSIONS

There are no data from randomized controlled trials on the impact of any form of treatment on the risk of progression from ocular to generalized myasthenia gravis. The available randomized controlled literature does not permit any meaningful conclusions about the efficacy of any form of treatment for ocular myasthenia. Data from several reasonably good quality observational studies suggest that corticosteroids and azathioprine may be beneficial in reducing the risk of progression to generalized myasthenia gravis.

Long-term follow-up after thymectomy for myasthenia gravis: thoracoscopic vs open

PURPOSE

The aim of this study was to determine if patients are in remission or weaning off medication after thymectomy for myasthenia gravis (MG) and to examine the thoracoscopic versus open approaches.

METHODS

A retrospective review of all patients who underwent thymectomy for MG at a tertiary referral center between 1992 and 2004 (N = 14). Six patients (42.9%) underwent thoracoscopic resection. Eight patients underwent open resection; 5 (35.7%) had median sternotomy and 3 (21.4%) by transcervical approaches. Follow-up was obtained in 12 (85.7%) of 14 patients by both chart review and telephone. The mean follow-up was 43.0 months (range, 4-111 months). Statistical significance was determined by Student's t test or Fisher's Exact Test.

RESULTS

The thoracoscopic group had a mean operating time of 138.8 minutes compared with 139.8 minutes in the open group (P = .9). The thoracoscopic group had a mean estimated blood loss of 7.5 mL compared with 52.5 mL in the open group (P = .02). The mean length of stay for the thoracoscopic group was 1.5 days (range, 1-2 days) and was 10.6 days (range, 3-41 days) in the open group (P = .13). Three (60%) of 5 patients were entirely off medication in the thoracoscopic group at the time of follow-up compared with 3 (50%) of 6 patients in the open group (P = 1.0). In the thoracoscopic group, 5 (83.3%) of 6 were in class 1 to 3 of the DeFilippi classification (complete remission or improved with decreased medication requirements). One patient had no change in symptoms (class 4). In the open group, 5 (83.3%) of 6 were classified as DeFilippi 1 to 3 at the time of follow-up, and one patient had worsening symptoms (class 5).

CONCLUSIONS

Both thoracoscopic and open approaches to thymectomy in patients with MG are effective, with more than 80% of patients in both groups in remission or with improvement at the time of follow-up. The thoracoscopic group has the added benefits of decreased estimated blood loss, decreased length of hospital stay, and improved cosmesis. We advocate the thoracoscopic approach for thymectomy in the treatment of juvenile MG.

Autoimmune channelopathies

Autoimmune disorders of the neuromuscular junction remain a paradigm for our understanding of autoimmunity. Since the role of autoantibodies to acetylcholine receptors in the pathogenesis of myasthenia gravis was first recognized in the 1970s, a range of antibody-mediated disorders of the neuromuscular junction have been described, each associated with an autoantibody to a specific ligand-gated receptor, voltage-gated ion channel or related protein. In addition, antibodies to a ganglionic form of acetylcholine receptor have been detected in autoimmune forms of autonomic neuropathy. In the past few years, a role for antibodies in disorders of the CNS has begun to emerge, challenging our previous concepts regarding the blood-brain barrier and the role of the humoral immune system in CNS pathology. Although it has not yet been definitively shown that these CNS conditions are antibody-mediated, the detection of the specific antibody supports a trial of immunosuppressive therapy to which many patients appear to respond. In this article, we review the roles of antibodies to receptors and ion channels in the peripheral and central nervous systems, concentrating on the recently defined autonomic and CNS conditions and on the role of antibody measurement in diagnosis and management.

Neuromuscular junction autoimmune disease: muscle specific kinase antibodies and treatments for myasthenia gravis

PURPOSE OF REVIEW

Some of the 20% of myasthenia gravis patients who do not have antibodies to acetylcholine receptors (AChRs) have antibodies to muscle specific kinase (MuSK), but a full understanding of their frequency, the associated clinical phenotype and the mechanisms of action of the antibodies has not yet been achieved. Moreover, some patients do not respond well to conventional corticosteroid therapy. Here we review recent clinical and experimental studies on MuSK antibody associated myasthenia gravis, and summarize the results of newer treatments for myasthenia gravis.

RECENT FINDINGS

MuSK antibodies are found in a variable proportion of AChR antibody negative myasthenia gravis patients who are often, but not exclusively, young adult females, with bulbar, neck, or respiratory muscle weakness. The thymus histology is normal or only very mildly abnormal. Surprisingly, limb or intercostal muscle biopsies exhibit no reduction in AChR numbers or complement deposition. However, patients without AChR or MuSK antibodies appear to be similar to those with AChR antibodies and may have low-affinity AChR antibodies. A variety of treatments, often intended to enable corticosteroid doses to be reduced, have been used in all types of myasthenia gravis with some success, but they have not been subjected to randomized clinical trials.

SUMMARY

MuSK antibodies define a form of myasthenia gravis that can be difficult to diagnose, can be life threatening and may require additional treatments. An improved AChR antibody assay may be helpful in patients without AChR or MuSK antibodies. Clinical trials of drugs in other neuroimmunological diseases may help to guide the treatment of myasthenia gravis.

The Role of the Thymus in the Pathogenesis of Myasthenia Gravis

Myasthenia gravis is an organ-specific autoimmune disease characterized by the production of anti-acetylcholine receptor antibodies. In this review, I describe the pathophysiological importance of the altered chemokine receptor-mediated signaling in the thymus and peripheral blood of myasthenia gravis patients. The epidemiological and clinical features of myasthenia gravis are also discussed.

[Diffuse primary leptomeningeal gliomatosis]

A woman died at the age of 22 years. Lifetime diagnosis had been inflammatory arachnopathy. The course of the disease had taken at least 6 years. Autopsy revealed primary diffuse leptomeningeal astrocytoma of the brain and spinal cord without neoplastic foci in the parenchyma of the central nervous system. Patchy dystrophic calcifications were recorded from the cerebral and cerebellar cortex.