Disease severity and outcome in thymoma myasthenia gravis: a long-term observation study

Disease-Based Prognostication: Myasthenia Gravis

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

Clinicodemographic characteristics and prognostic role of myasthenia gravis in thymoma: Experience from a Saudi population

OBJECTIVES

The objectives of the study were to determine the clinicodemographic characteristics and the prognostic role of myasthenia gravis (MG) in thymoma.

METHODS

The records of patients who underwent surgical resection of thymoma at King Faisal Specialist Hospital and Research Center in the past 23 years were reviewed. Seventy thymoma patients were finally included and were then categorized based on MG status into the MG group (39 patients) and the non-MG group (31 patients). Collected data included patients' demographic characteristics, tumor characteristics, and postoperative clinical outcomes. All analyses were conducted using SPSS. The comparison between both groups was tested using the Student t-test and Chi-square test for continuous and categorical variables, respectively. A P = 0.05 or less indicated statistical significance.

RESULTS

Patients' age ranged from 11 to 76 years, and female predominance was observed (55.7%). Compared to the non-MG group, no difference in patients' gender was observed (P = 0.058); however, MG patients had a younger age (39.30 vs. 48.77, P = 0.0095). No difference was noted between both groups based on the World Health Organization classification (P = 0.398), but MG patients tended to present with less-advanced tumors based on the TNM classification (P = 0.039) and lower stage based on the MASAOKA staging system (P = 0.017). No significant change in tumor size (P = 0.077), resectability (P = 0.507), and adjuvant therapy (P = 0.075) were observed. MG was not significantly associated with postoperative complications, morbidity, or mortality. However, it exhibited a prognostic protective role in terms of lower recurrence (2.56% vs. 35.48%, P = 0.0001) and longer survival duration (18.62 vs. 10.21 years, P < 0.001) as compared to non-MG patients.

CONCLUSIONS

MG occurrence in thymoma patients is more likely to occur at a younger age, higher TNM classification, and advanced MASAOKA stage. Although no significant association was noted between MG and complications and mortality, MG exhibited a protective role in thymoma by providing a lower recurrence rate and longer survival duration.

Iron metabolism in non-anemic myasthenia gravis patients: A cohort study

BACKGROUND

The association of iron metabolism parameters with disease severity and outcome in myasthenia gravis (MG) patients has not been reported. This study was conducted to determined clinical factors including iron metabolism parameters correlated with disease severity and future outcome in non-anemic immunotherapy-naïve MG patients first receiving immunotherapy.

MATERIAL AND METHODS

One hundred and ten patients were included at baseline to explore predictor variables associated with disease severity represented by variables derived from MG activities of daily living (MG-ADL) score using multivariate logistic regression, after which 103 and 98 patients were included respectively in multivariate survival analyses at 6-month and 12-month follow-up to identify predictors for minimal manifestation status (MMS) after starting immunotherapy.

RESULTS

Higher ferritin level was independently associated with higher risk of severe generalized disease in non-anemic immunotherapy-naïve MG patients. Total iron binding capacity <250 μg/dL and the interval between onset and immunotherapy <1 year were independent predictors for MMS at 6-month and 12-month follow-up after initiating immunotherapy. Transferrin <2.00 g/L was an independent predictor for MMS at 12-month follow-up.

CONCLUSION

Iron metabolism parameters might be promising biomarkers for evaluating disease severity and guiding therapeutic decision in MG patients.

Anti-titin antibody is associated with more frequent hospitalization to manage thymoma-associated myasthenia gravis

BACKGROUND AND PURPOSE

Anti-titin antibodies are antistriational antibodies associated with thymoma-associated myasthenia gravis (MG). We evaluated whether the patients with anti-titin antibody are more frequently hospitalized to manage thymoma-associated MG than those patients without anti-titin antibody.

METHODS

Patients with thymoma-associated MG who conducted the serological test for anti-titin antibody were retrospectively included. Disease severity, treatments, MG-related annual hospitalization rate, and MG-related emergency room (ER) visit rate were compared between the patients with anti-titin antibody and those patients without anti-titin antibody. Multivariate analysis was conducted to analyze the association between anti-titin antibody serostatus and multiple admissions (hospitalization or ER visit of ≥2 times).

RESULTS

Of the 64 included patients, 31 (48.4%) patients were positive for anti-titin antibody (titin+ group) and 33 (51.6%) patients were negative for anti-titin antibody (titin- group). Both the annual rate of MG-related hospitalization and ER visit were significantly higher in the titin+ group [0.2 (0.1-0.6) and 0.1 (0-0.2) per year, respectively] than those in the titin- group [0 (0-0.2) and 0 (0-0) per year, p = 0.004 and p = 0.006, respectively]. In multivariate analysis, positive anti-titin antibody was still significantly associated with multiple admissions [odds ratio (OR) 4.11, 95% CI 1.05-16.03] compared to the titin- group as a reference after adjusting for sex, follow-up duration, age at onset, systemic chemotherapy, and the Masaoka staging.

CONCLUSION

The presence of anti-titin antibody is associated with more frequent hospital utilization. Personalized explanation and careful monitoring strategy could be required in patients with thymoma-associated MG with anti-titin antibody for the timely detection of relapses.

Characterization of the nicotinic acetylcholine receptor antibodies after an unexpected increase of antibody titer in thymoma associated myasthenia gravis patients

Two thymoma-associated myasthenia gravis patients with chronic well-controlled disease but an unexpected increase in anti-nAChR autoantibodies titer are reported. The specificity of anti-nAChR autoantibodies directed against extracellular parts of the receptor was studied in order to investigate the discrepancy between clinical and immunological status. Analysis of the anti-nAChR autoantibodies recognizing the extracellular parts of the nAChR revealed that when the concentration of anti-nAChR autoantibodies titer increased both patients had non-anti-α1 autoantibodies. Since the clinical profile of both patients remained unchanged, the increase of non-anti-α1 autoantibodies did not affect the 2 patients' disease progression. Thus, immunotherapy modification due to an increase of anti-nAChR autoantibodies titer could be erroneous and potentially harmful.

Ocular myasthenia gravis: a review and practical guide for clinicians

Myasthenia gravis is a rare autoimmune disease characterised by autoantibodies preventing normal function of acetylcholine receptors at the post-synaptic membrane of the neuromuscular junction. This causes weakness of skeletal muscles that can be variable and fatigable, and often manifests as ptosis and/or diplopia, with 60% of patients demonstrating ocular features at onset, and thus may present initially to eye care practitioners. Approximately 15% of patients have ocular myasthenia gravis, where symptoms remain restricted to this distribution. The majority of patients have blocking antibodies against the acetylcholine receptor, but antibodies directed against other related targets account for a smaller proportion and are associated with specific phenotypes. Associations with both thymoma and with other autoimmune phenomena (particularly thyroid disease) can occur. Clinical examination can identify characteristic findings including fatigable ptosis and Cogan's lid twitch sign. Investigations to confirm the diagnosis include simple office-based procedures such as the ice test, and testing for serum autoantibodies, as well as electrophysiological testing such as repetitive nerve stimulation and single-fibre electromyography. The management of ocular myasthenia gravis is discussed, including non-pharmacological options, pyridostigmine, corticosteroids, other immunosuppressive agents, and thymectomy. The goals of management are to alleviate symptoms, and where possible prevent chronic disability or progression to generalised myasthenia gravis.

A Stable Cell Line Expressing Clustered AChR: A Novel Cell-Based Assay for Anti-AChR Antibody Detection in Myasthenia Gravis

Cell-based assays (CBAs) and radioimmunoprecipitation assay (RIPA) are the most sensitive methods for identifying anti-acetylcholine receptor (AChR) antibody in myasthenia gravis (MG). But CBAs are limited in clinical practice by transient transfection. We established a stable cell line (KL525) expressing clustered AChR by infecting HEK 293T cells with dual lentiviral vectors expressing the genes encoding the human AChR α1, β1, δ, ϵ and the clustering protein rapsyn. We verified the stable expression of human clustered AChR by immunofluorescence, immunoblotting, and real-time PCR. Fluorescence-activated cell sorting (FACS) was used to detect anti-AChR antibodies in 103 MG patients and 58 healthy individuals. The positive results of MG patients reported by the KL525 was 80.6% (83/103), 29.1% higher than the 51.4% (53/103) of RIPA. 58 healthy individuals tested by both the KL525 CBA and RIPA were all negative. In summary, the stable expression of clustered AChR in our cell line makes it highly sensitive and advantageous for broad clinical application in CBAs.

Prevalence and risk factors of myasthenia gravis recurrence post-thymectomy

Objectives:

To evaluate the prevalence and the factors associated with recurrence of myasthenia gravis following thymectomy.

Methods:

Six electronic databases which reported on recurrence of myasthenia gravis following thymectomy and/or its risk factors from 1985 to 2018 were searched. Summary prevalence and risk values obtained based on the random effect models were reported.

Results:

Seventy (70) papers containing 7,287 individuals with myasthenia gravis who received thymectomy as part of their management were retrieved. The patients had a mean follow-up of 4.65 years post-thymectomy. The prevalence of myasthenia gravis recurrence post-thymectomy was 18.0% (95% CI 14.7–22.0%; 1865/7287). Evident heterogeneity was observed (I²=93.6%; p<0.001). Recurrence rate was insignificantly higher in male compared with female patients (31.3 vs. 23.8%; p=0.104). Pooled recurrence rates for thymomatous (33.3%) was higher than the rate among non-thymomatous (20.8%) myasthenia gravis patients (Q=4.19, p=0.041). Risk factors for recurrence include older age, male sex, disease severity, having thymomatous myasthenia gravis, longer duration of the myasthenia gravis before surgery, and having an ectopic thymic tissue.

Conclusion:

A fifth of individuals with myasthenia gravis experience recurrence after thymectomy. Closer monitoring should be given to at-risk patients and further studies are needed to understand interventions to address these risks.

Long-term outcomes and prognostic factors in generalized myasthenia gravis

OBJECTIVE

This study aimed to investigate the timing of meeting the criteria for a status of "minimal manifestation (MM) or better" and the factors that influenced whether "MM or better status" or "MM or better status with an oral prednisolone (PSL) dose of 5 mg/day or less (5-mg MM)" was met in patients with acetylcholine receptor (AChR) antibody-positive generalized myasthenia gravis (MG).

METHODS

We performed a retrospective study in 93 patients with AChR antibody-positive generalized MG who were followed for 3 years after the start of immunotherapy. We reviewed clinical data, such as MG-related symptoms, the MG activities of daily living profile (MGADL) score, immunotherapy including the dose of PSL, and achievement of the status of MM or better at baseline and 3, 6, 12, 24, and 36 months after treatment.

RESULTS

An MM or better status was achieved in 60% of the patients 3 months and in 90% of the patients 2 years after initiating immunotherapy. At 2 years, 60% of the patients had achieved the treatment goal, which was an "5-mg MM". More frequent plasmapheresis and higher dose of PSL within 3 months after immunotherapy initiation were associated with difficulty in achieving the 5-mg MM status at 2 years.

CONCLUSION

Approximately 60% of the MG patients achieved the treatment goal within 2 years after treatment. PSL dose and the cumulative number of plasmapheresis procedures at 3 months after immunotherapy initiation may help identify treatment-resistant patients with MG.

Onset and Evolution of Clinically Apparent Myasthenia Gravis After Resection of Non-myasthenic Thymomas

Patients with thymoma and without clinical or electromyographical myasthenic signs may occasionally develop myasthenia several years after thymectomy. Hereby, we investigated the predictors and the evolution of this peculiar disease. We performed a retrospective analysis in 104 consecutive patients who underwent thymectomy between 1987 and 2013 for thymoma without clinical or electromyographic signs of myasthenia gravis. Predictors of post-thymectomy onset of myasthenia gravis were investigated with univariate time-to-disease analysis. Evolution of myasthenia was analyzed with time-to-regression analysis. Eight patients developed late myasthenia gravis after a median period of 33 months from thymectomy. No significant correlation was found for age, gender, Masaoka's stage, and World Health Organization histology. Only high preoperative serum acetylcholine-receptor antibodies titer (>0.3 nmol/L) was significantly associated with post-thymectomy myasthenia gravis at univariate time-to-disease (P = 0.003) analysis. Positron emission tomography was always performed in high-titer patients, and increased metabolic activity was detected in 4 of these patients. Surgical treatment through redo-sternotomy or video-assisted thoracoscopy was performed in these last cases with a remission in all patients after 12, 24, 32 and 48 months, respectively. No patient under medical treatment has yet developed a complete remission. In our study the presence of preoperative high-level serum acetylcholine receptor antibodies was the only factor significantly associated with the development of post-thymectomy myasthenia gravis. The persistence of residual islet of ectopic thymic tissue was one of the causes of the onset of myasthenia and its surgical removal was successful.

Gender and quality of life in myasthenia gravis patients from the myasthenia gravis foundation of America registry

INTRODUCTION

Quality of life (QOL) has been poorly characterized among patients with myasthenia gravis (MG) other than assessments performed within the clinical setting.

METHODS

Patients age ≥ 18 years who were diagnosed with MG and registered with the MG patient registry between July 1, 2013, and June 30, 2016, were included. Demographic information, disease related history, and QOL were compared between men and women using multivariable analysis.

RESULTS

A total of 1,315 subjects (827 women) were included. Women were significantly younger, had a younger age at symptom onset, and were more likely to have thymoma and thymectomy. The 15-item Myasthenia Gravis Quality of Life scale (MG-QOL15) was significantly worse in women. MG-QOL15 score was comparable between women who had thymectomy and men with or without thymectomy.

DISCUSSION

QOL among MG patients is worse in women compared with men, but this disparity is eliminated in women who have undergone thymectomy. Muscle Nerve, 2018.

Metastatic Thymoma-Associated Myasthenia Gravis: Favorable Response to Steroid Pulse Therapy Plus Immunosuppressive Agent

BACKGROUND Our study retrospectively reviewed the therapeutic effect of steroid pulse therapy in combination with an immunosuppressive agent in myasthenia gravis (MG) patients with metastatic thymoma. MATERIAL AND METHODS MG patients with metastatic thymoma that underwent methylprednisolone pulse therapy plus cyclophosphamide were retrospectively analyzed. Patients initially received methylprednisolone pulse therapy followed by oral methylprednisolone. Cyclophosphamide was prescribed simultaneously at the beginning of treatment. Clinical outcomes, including therapeutic efficacy and adverse effects of MG and thymoma, were assessed. RESULTS Twelve patients were recruited. According to histological classification, 4 cases were type B2 thymoma, 3 were type B3, 2 were type B1, and 1 was type AB. After combined treatment for 15 days, both the thymoma and MG responded dramatically to high-dose methylprednisolone plus cyclophosphamide. The symptoms of MG were improved in all patients, with marked improvement in 6 patients and basic remission in 4. Interestingly, complete remission of thymoma was achieved in 5 patients and partial remission in 7 patients. Myasthenic crisis was observed in 1 patient and was relieved after intubation and ventilation. Adverse reactions were observed in 7 patients (58.3%), most commonly infections, and all were resolved without discontinuation of therapy. During the follow-up, all patients were stabilized except for 1 with pleural metastasis who received further treatment and another 1 who died from myasthenic crisis. CONCLUSIONS The present study in a series of MG patients with metastatic thymoma indicated that steroid pulse therapy in combination with immunosuppressive agents was an effective and well-tolerated for treatment of both metastatic thymoma and MG. Glucocorticoid pulse therapy plus immunosuppressive agents should therefore be considered in MG patients with metastatic thymoma.

A Case Series of Patients With Autoimmune Myasthenia Gravis in Association With Invasive Thymoma

OBJECTIVES

In some patients, autoimmune myasthenia gravis (MG) is associated with thymic hyperplasia or thymoma, and in some patients the thymoma is invasive. Little is known about the clinical course of subjects who present with MG and are found to have invasive thymoma.

METHODS

We reviewed the patients at our clinic with MG and invasive thymoma, and have described their clinical features.

RESULTS

Six MG patients were diagnosed with invasive thymoma. The subjects had extensive multimodal therapy. Two subjects died from uncontrolled neuromuscular respiratory failure despite aggressive immunosuppression, 2 subjects had other autoimmune disorders (Morvan syndrome and polymyositis), and 2 subjects are controlled on immunosuppression.

CONCLUSIONS

Patients with invasive thymoma and MG can have a poor outcome, with difficulty in controlling myasthenic symptoms and can have other clinically important autoimmune diseases.

An up-date on health-related quality of life in myasthenia gravis -results from population based cohorts

Abstract

Current available therapies control Myasthenia gravis (MG) reasonably well, but Health Related Quality of life (HRQOL) remains lower than expected. The aim was provide insights in how HRQOL in MG stands across borders and time, compare the scores to general population controls and other chronic disorders and assess the impact of potential predictors for quality of life such as a) clinical characteristics b) antibodies c) thymoma and d) treatment in a population-based cohort.

Methods

We designed a population-based cross-sectional study including 858 patients, 373 from Norway and 485 from the Netherlands. The Short Form Health Survey 36 (SF-36) and a cross-cultural validated questionnaire were used. Data were in addition compared to the general population, other chronic diseases and previous studies.

Results

Mean physical composite score was 59.4 and mental composite score 69.0 with no differences between the countries. The mean HRQOL score was lower in patients with bulbar and generalized symptoms (p < 0.001) compared to sex and age adjusted healthy controls, but not in patients with ocular symptoms or patients in remission. Multivariate analysis revealed that female gender, generalized symptoms and use of secondary immunosuppressive drugs at the time of testing were risk factors for reduced HRQOL.

Conclusions

Remission and absence of generalized symptoms were favorable factors for HRQOL in MG patients. Historically, the HRQOL levels have not changed since 2001 and no new clinical predictors could be detected in this exhaustive population-based study. Further studies should explore the impact of non clinical factors like ethnic variations, socio-economic and hormonal factors on HRQOL.

Electronic supplementary material

The online version of this article (doi:10.1186/s12955-015-0298-1) contains supplementary material, which is available to authorized users.

Myasthenia gravis epidemiology in a national cohort; combining multiple disease registries

OBJECTIVES

There is a wide variation in reported prevalence and incidence of myasthenia gravis (MG). In this study, we aimed to evaluate the validity of two nationwide databases by comparing prevalence and incidence rates reported from three recent studies using the two databases as case-finding method.

MATERIALS AND METHODS

Two different Norwegian nationwide databases were used: the acetylcholine receptor antibody database (reference cohort) and the Norwegian Prescription Database (NorPD) (study cohort). Presence of acetylcholine receptor antibodies (AChR) is specific for MG. Up to 85% of MG patients are AChR antibody-positive. All samples from the whole country were tested at one laboratory. NorPD contains patient information on all prescriptions of pyridostigmine.

RESULTS

Prevalence was 131 per million in the study cohort and 145 per million estimated from the reference cohort (Jan 1, 2008). No significant difference in prevalence between the study cohort and the reference cohort was found (SIR 1.1, 95% CI 1.0-1.2). The annual incidence rate was 16.0 per million in the study cohort and 8.8 per million estimated from the reference cohort, twofold more new MG patients were found in the study cohort compared to estimated figures from the reference cohort (SIR 1.8; 1.4-2.3).

CONCLUSIONS

This study confirms an optimal and unbiased case finding in both databases. Our calculated prevalence and incidence rates are in line with previous population-based studies. There was good agreement in prevalence reported from the two databases. The discrepancy in incidence is expected to diminish as years of study are increasing in NorPD.

Antititin antibody in early- and late-onset myasthenia gravis

OBJECTIVES

Myasthenia gravis (MG) is an autoimmune disease caused by antibodies against neuromuscular junction proteins, 85% of patients have antibodies against acetylcholine receptor (AChR-MG). Antititin antibodies are present in a subset of patients with MG. We aimed to determine the value of antititin antibodies as severity markers and thymoma predictors in early- and late-onset MG.

MATERIALS & METHODS

Two-hundred and ninety-five consecutive MG patients (188 F and 107 M) aged 12-89 years (mean 50y) were included. 164 patients had early-onset (EOMG, ≤50 years of age), 131 had late-onset MG (LOMG). Twenty-six patients had thymoma. symptoms, severity graded with MGFA scale, thymus histology, medications, and treatment results were analyzed.

RESULTS

Antititin antibodies were present in 81 (27%) of all patients: 54% of thymoma MG, 0.6% of non-thymomatous EOMG, and 55% of LOMG, with proportion of titin-positive patients increasing linearly from 40% in the 6th to 88% in the 9th decade of life. Titin-positive patients had more bulbar symptoms (P = 0.003). Severity of MG, need for immunosuppression, myasthenic crisis risk or treatment results were not related to its presence. Antititin antibodies had 56% sensitivity, 99% specificity, 90% positive predictive value (PPV), and 95% negative predictive value (NPV) for thymoma diagnosis in EOMG, and 50% sensitivity, 75% specificity, 71% PPV and 55% NPV in LOMG.

CONCLUSIONS

Antititin antibodies have high PPV and NPV for thymoma in EOMG. In MG without thymoma, antititin antibodies can be considered as markers of LOMG, but not of a severe course in our MG cohort.

The myasthenic patient in crisis: an update of the management in Neurointensive Care Unit

Myasthenia gravis (MG) is an autoimmune disorder affecting neuromuscular transmission leading to generalized or localized muscle weakness due most frequently to the presence of autoantibodies against acetylcholine receptors in the postsynaptic motor end-plate. Myasthenic crisis (MC) is a complication of MG characterized by worsening muscle weakness, resulting in respiratory failure that requires intubation and mechanical ventilation. It also includes postsurgical patients, in whom exacerbation of muscle weakness from MG causes a delay in extubation. MC is a very important, serious, and reversible neurological emergency that affects 20-30% of the myasthenic patients, usually within the first year of illness and maybe the debut form of the disease. Most patients have a predisposing factor that triggers the crisis, generally an infection of the respiratory tract. Immunoglobulins, plasma exchange, and steroids are the cornerstones of immunotherapy. Today with the modern neurocritical care, mortality rate of MC is less than 5%.

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.

Thymus pathology observed in the MGTX trial

The MGTX trial is the first prospective, randomized clinical trial that aims to evaluate the impact of extended transsternal thymectomy on myasthenic symptoms, prednisone requirements, and quality of life in patients with nonthymomatous, anti-acetylcholine receptor autoantibody-positive myasthenia gravis (MG). Here, we give an overview of the rationale of thymectomy and the standardized macroscopic and histopathological work-up of thymectomy specimens as fixed in MGTX standard operating procedures, including the grading of thymic lymphofollicular hyperplasia and the morphometric strategy to assess thymic involution.

Thymoma in myasthenia gravis: from diagnosis to treatment

One half of cortical thymoma patients develop myasthenia gravis (MG), while 15% of MG patients have thymomas. MG is a neuromuscular junction disease caused in 85% of the cases by acetylcholine receptor (AChR) antibodies. Titin and ryanodine receptor (RyR) antibodies are found in 95% of thymoma MG and 50% of late-onset MG (MG onset ≥50 years), are associated with severe disease, and may predict thymoma MG outcome. Nonlimb symptom profile at MG onset with bulbar, ocular, neck, and respiratory symptoms should raise the suspicion about the presence of thymoma in MG. The presence of titin and RyR antibodies in an MG patient younger than 60 years strongly suggests a thymoma, while their absence at any age strongly excludes thymoma. Thymoma should be removed surgically. Prethymectomy plasmapheresis/iv-IgG should be considered before thymectomy. The pharmacological treatment does not differ from nonthymoma MG, except for tacrolimus which is an option in difficult thymoma and nonthymoma MG cases with RyR antibodies.

Three types of striational antibodies in myasthenia gravis

Myasthenia gravis (MG) is caused by antibodies that react mainly with the acetylcholine receptor on the postsynaptic site of the neuromuscular junction. A wide range of clinical presentations and associated features allow MG to be classified into subtypes based on autoantibody status. Striational antibodies, which react with epitopes on the muscle proteins titin, ryanodine receptor (RyR), and Kv1.4, are frequently found in MG patients with late-onset and thymoma. Antititin and anti-RyR antibodies are determined by enzyme-linked immunosorbent assay or immunoblot. More recently, a method for the detection of anti-Kv1.4 autoantibodies has become available, involving 12-15% of all MG patients. The presence of striational antibodies is associated with more severe disease in all MG subgroups. Anti-Kv1.4 antibody is a useful marker for the potential development of lethal autoimmune myocarditis and response to calcineurin inhibitors. Detection of striational antibodies provides more specific and useful clinical information in MG patients.

Myasthenia gravis requiring pyridostigmine treatment in a national population cohort

BACKGROUND

Pyridostigmine is the first drug of choice for patients with myasthenia gravis (MG). The drug is not prescribed regularly to any other patient groups. We aimed to determine the prevalence, incidence and gender-specific characteristics of patients with MG needing drug treatment in a well-defined population cohort.

METHODS

Data were retrieved from the Norwegian Prescription Database (NorPD) 2004-2007, containing information on all dispensed drugs in Norway. The study population comprised 677 recipients of pyridostigmine who met the following inclusion criteria (one or more): (i) More than one prescription 1 January 2004-31 December 2007, (ii) prescription from a specialist in neurology, (iii) prescription for MG being specified in NorPD.

RESULTS

A total of 435 (64%) women and 242 men were included; female:male ratio 1.8:1. Point prevalence (1 January 2008) of symptomatic MG was 131 per million; 92 for men, 170 for women. Seventy-four new users of pyridostigmine were registered in 2007 (42 women, 32 men), i.e. the incidence rate for 2007 being 16 per million; 14 for men, 18 for women. Mean age of incident cases was 59 years; 64 and 55 years, respectively. Prevalence and incidence were significantly higher in the age group ≥ 50 years than < 50 years (P < 0.001), and highest at 70-79 years. Prevalence and incidence did not differ in the five geographical health regions in Norway.

CONCLUSIONS

Reported prevalence and incidence are amongst the highest found in similar studies. This may be explained by optimal case identification, higher incidence of drug requiring MG amongst the elderly, and recurrences of previous MG.

Management of myasthenic patients with thymoma

Myasthenia gravis (MG) associated with thymomas differs from nonthymomatous MG, and thymomas associated with MG are also different from non-MG thymomas. According to the World Health Organization classification, the incidence of MG in thymomas was the highest in the subtypes B2, B1, and AB. Transsternal approach is still regarded as the gold standard for surgical treatment of thymomas. Less-invasive techniques of thymectomy are promising, but it is too early to estimate their real oncological value. In the series including more than 100 patients, the prognosis for survival is better in patients with thymomas associated with MG than in those with non-MG thymomas, and the prognosis for patients with MG associated with thymoma is worse than that for patients with nonthymomatous MG.

Autoimmune myasthenia gravis: emerging clinical and biological heterogeneity

Acquired myasthenia gravis (MG) is an autoimmune disorder of the neuromuscular junction in which patients experience fluctuating skeletal muscle weakness that often affects selected muscle groups preferentially. The target of the autoimmune attack in most cases is the skeletal muscle acetylcholine receptor (AChR), but in others, non-AChR components of the neuromuscular junction, such as the muscle-specific receptor tyrosine kinase, are targeted. The pathophysiological result is muscle endplate dysfunction and consequent fatigable muscle weakness. Clinical presentations vary substantially, both for anti-AChR positive and negative MG, and accurate diagnosis and selection of effective treatment depends on recognition of less typical as well as classic disease phenotypes. Accumulating evidence suggests that clinical MG subgroups might respond differently to treatment. In this Review, we provide current information about the epidemiology, immunopathogenesis, clinical presentations, diagnosis, and treatment of MG, including emerging therapeutic strategies.

Microscopic polyangiitis and myasthenia gravis: the battle of Occam and Hickam

Microscopic polyangiitis (MPA) is a pauci-immune, necrotising, small-vessel vasculitis with an incidence of 3.6 per million population that typically presents in adulthood. Myasthenia gravis (MG), the most common disorder of the neuromuscular junction is rare, with an incidence of four per million population. We present the case of an adolescent girl previously diagnosed with MPA at age 7 years who presented with breathlessness and respiratory failure aged 15 years. The respiratory symptoms were due to thymoma-MG, which was successfully treated with cholinesterase inhibitors and thymectomy. This case report illustrates that the well-established doctrines of Occam's razor and of 'common conditions occurring commonly' are not universally applicable, and that in the adolescent age group, one should still consider Hickam's dictum.

Myasthenia gravis: disease severity and prognosis

OBJECTIVES

To examine myasthenia gravis (MG) severity and long-term prognosis in seronegative, seropositive, and thymoma MG.

MATERIALS AND METHODS

Four series of patients were studied retrospectively. Severity and treatment were assessed each year, and muscle antibodies were assayed.

RESULTS

Seropositive MG patients had a more severe course than seronegative MG patients. MG severity was higher in non-thymectomized compared to thymectomized early-onset MG patients. MG severity did not differ between thymectomized and non-thymectomized late-onset patients. There was no significant difference in MG severity between thymoma and non-thymoma MG patients.

CONCLUSIONS

MG is more severe in seropositive MG patients. With proper treatment, especially early thymectomy, the long-term prognosis is good in seropositive MG patients. The present studies indicate a benefit of thymectomy in early-onset MG, but no dramatic benefit in late-onset MG. Similar MG severity and outcome was seen in thymoma and non-thymoma MG.

Causes of death among patients with myasthenia gravis in Norway between 1951 and 2001

OBJECTIVE

This study investigated the causes of death among patients with myasthenia gravis (MG), with emphasis on respiratory tract and cardiac disease.

METHODS

The Norwegian Cause of Death Register contains information on all deaths among Norwegian citizens. In total, 249 deceased patients with MG were identified (1951-2001). These were compared with 1245 controls deceased in the same period and matched for sex and year of birth.

RESULTS

The death certificates of patients with MG had a significantly higher occurrence of respiratory tract disease as cause of death than controls (28.1% v 20.9%, p = 0.012). The difference was most pronounced for male patients, for patients dying between 30 and 69 years of age, and for deaths occurring before 1996. For cardiac disease there was a significantly lower occurrence among patients with MG than among controls at 50-69 years of age, for both men (19.4% v 52.0%, p = 0.001) and women (14.6% v 29.6%, p = 0.036). Age and year of death were important determinants for the causes of death, but could not account for the differences between the patients with MG and controls.

CONCLUSIONS

This study shows that patients with MG dying between 1951 and 1995 had a higher occurrence of respiratory tract disease listed as cause of death than had a matched control group. The lack of difference after 1995 probably reflects improved treatment of MG and its complications. The reduced occurrence of cardiac disease among patients with MG is probably explained by competing factors (respiratory tract disease) causing death.

Myasthenia gravis: clinical, immunological, and therapeutic advances

We give an update on clinical, immunological, and therapeutic advances in the field of myasthenia gravis, including a summary of suggested therapeutic recommendations.