The predictive value of the presence of different antibodies and thymus pathology to the clinical outcome in patients with generalized myasthenia gravis

Galactosylation of serum immunoglobulin G in myasthenia gravis with different autoantibodies

Myasthenia gravis (MG) is a disease with impaired transmission at the neuromuscular junction, characterised by weakness and fatigability of skeletal muscles. In acquired autoimmune MG, antibodies against acetylcholine receptor (AChRAb) or muscle-specific tyrosine kinase (MuSKAb) are present. There is not much data about immunoglobulin G (IgG) galactosylation in MG, and none based on interactions with lectins. This study aims to examine IgG galactosylation in two types of myasthenia, using affinity immunoelectrophoresis with lectin concanavalin A (Con A). Affinity of Con A-IgG interaction, expressed as retardation coefficient (R), indicated the presence of degalactosylated IgG. The average R values were significantly different between three examined groups, being the lowest in controls (healthy subjects), higher in acetylcholine receptor (AChR) MG, and the highest in muscle-specific tyrosine kinase (MuSK) MG (ANOVA, p < .05). This indicated decreased galactosylation of IgG in both types of MG compared to controls, more pronounced in MuSK MG. IgG galactosylation was also investigated in relation to the disease severity score, determined according to the Myasthenia Gravis Foundation of America (MGFA) criteria, at the time of diagnosis, nadir of the disease and last check-out visit. The average R values for mild disease (stages I-IIIa) were significantly lower than for severe disease (stages IIIb-V), both at the time of diagnosis (p < .05), and at the nadir of the disease (p < .05). Thus, IgG galactosylation was associated with the presence of specific autoantibodies in MG, as well as with disease severity for both types of MG, and may be a predictive marker of MG outcome.

Therapeutic and prognostic features in myasthenia gravis patients followed in a tertiary neuromuscular diseases center in Turkey

Introduction

In this study, we aim to evaluate the treatment responses and prognostic characteristics of Myasthenia Gravis (MG) patients followed in a tertiary neuromuscular diseases center in Turkey.

Methods

One hundred seventy four MG patients (between years 2011 and 2022) in Antalya, Turkey were diagnosed, and evaluated on a classification of MG was based on Myasthenia. Gravis Foundation of America (MGFA) clinical classification. Exclusion of other possible diseases in the differential diagnosis and support by beneficial response to treatment with acetylcholinesterase inhibitors were also taken into consideration.

Results

Mean age of participants was 54.86 (SD = 14.856; min-max = 22-84). Ninety (51.7%) were female. MG was more common in women under the age of 65 (58%) and in men over the age of 65 (64%). Generalized MG was seen in 75.3% of the patients. Anti-AChR positivities were detected in 52.3%, Anti-MuSK positivity in 4.6%, and seronegativity in 22.4%. Thymoma was detected in nearly 9.8% and thymectomy was performed in 28.7 percent. Most of the patients (57.5%) were using corticosteroids. Azathioprine was used by 39% and mycophenolate mofetil by 10.3% of patients. Mortality was higher and disease was more severe in late-onset (>50 years) MG patients (especially in the COVID-19 pandemic). Eight patients (four women, four men, mean age 75.5 years) died during follow-up. None of them died due to myasthenic worsening, two died due to malignancy and two due to infection. During the COVID pandemic, 16 patients (9.2%) had COVID infection. Four patients died due to COVID-19 infection, these four patients had serious comorbidities, and three of them were elderly (>75 years).

Conclusion

In conclusion, MG is more common in women between the ages of 20-40 and in men over the age of 65. The use of corticosteroids was more common under the age of 50, and the use of non-steroidal immunosuppressant agents was more common over the age of 50. Thymectomy is still an important supportive treatment approach in anti-AChR positive and seronegative generalized patients under 50 years of age. IVIG and plasmapheresis are effective treatments during acute exacerbations and bridging periods of treatments. Specific treatments are needed especially for resistant group of patients.

Childhood-Onset Myasthenia Gravis Patients Benefited from Thymectomy in a Long-Term Follow-up Observation

INTRODUCTION

 The effect of thymectomy on the treatment of childhood-onset myasthenia gravis (CMG) remains debatable. The objective of this study was to evaluate the clinical outcome and relevant prognostic factors of thymectomy for CMG patients.

MATERIALS AND METHODS

 A total of 32 CMG patients who underwent thymectomy before 18 years of age were included in this retrospective study. Clinical state following thymectomy was assessed by quantified myasthenia gravis (QMG) scores, myasthenia gravis-related activities of daily living (MG-ADL) scores, and Myasthenia Gravis Foundation of America postintervention status. Repeated-measures analysis of variance (ANOVA) examined the changes in postoperative scores during the 5-year follow-up. Univariate logistic regression was applied to identify factors associated with short-term (1-year postoperation) and long-term (5-year postoperation) clinical outcomes.

RESULTS

 Repeated-measures ANOVA showed that QMG scores (F = 6.737, p < 0.001) and MG-ADL scores (F = 7.923, p < 0.001) decreased gradually with time. Preoperative duration (odds ratio [OR] = 0.85, 95% confidence interval [CI]: 0.73-1.00, p = 0.043), gender (OR = 0.19, 95% CI: 0.04-0.94, p = 0.041), and MG subgroup (OR = 13.33, 95% CI: 1.43-123.99, p = 0.023) were predictors for 1-year postoperative prognosis. Shorter disease duration (OR = 0.82, 95% CI: 0.70-0.97, p = 0.018) and generalized CMG (OR = 6.11, 95% CI: 1.06-35.35, p = 0.043) were found to have more favorable long-term results.

CONCLUSION

 Our results suggest that thymectomy is effective in treating CMG. Thymectomy could be recommended for CMG patients, especially for patients in the early course of GMG.

Differential response to rituximab in anti-AChR and anti-MuSK positive myasthenia gravis patients: a single-center retrospective study

BACKGROUND

B-cell targeted therapy with rituximab has shown durable response in treating refractory myasthenia gravis (MG). This study compares the response to rituximab between patients with acetylcholine receptor autoantibody positive (AChR+) and muscle-specific kinase autoantibody positive (MuSK+) MG.

METHODS

This retrospective study included 33 patients with either AChR+ or MuSK+ MG who were treated with rituximab from 05/31/2003 to 05/31/2017. Pretreatment and post-treatment immunotherapy regimens, clinical symptoms, and examination findings were evaluated.

RESULTS

Median MGFA Class of II at baseline improved to an asymptomatic median classification at 12-months and last follow-up (p-values <.001) post-rituximab. Improvement in MGFA class was not significantly different between the groups. Twenty-one patients achieved clinical remission (12/17 AChR+, 9/16 MuSK+) with time to remission of 441.4 ± 336.6 days for AChR+ versus 230 ± 180.8 days for MuSK+ patients (p-value 0.049). The mean prednisone dosage requirement decreased significantly in both groups post-rituximab. AChR+ patients required more hospitalizations for exacerbation post-rituximab (p-value 0.046).

CONCLUSION

Rituximab treatment response is observed in both AChR+ and MuSK+ patients supporting the role of B cell depletion in the management of MG. While there was no significant difference between these groups in terms of clinical improvement, symptom-free state, and prednisone burden, MuSK+ MG patients may experience greater benefits, including earlier time to remission, fewer exacerbations and hospitalizations post-treatment.

Factors affecting outcome in ocular myasthenia gravis

AIM OF THE STUDY

50%-60% of patients with ocular myasthenia gravis (OMG) progress to generalized myasthenia gravis (GMG) within two years. The aim of our study was to explore factors affecting prognosis of OMG and to test the predictive role of several independent clinical variables.

MATERIALS AND METHODS

We reviewed a cohort of 168 Caucasian patients followed from September 2000 to January 2016. Several independent variables were considered as prognostic factors: gender, age of onset, results on electrophysiological tests, presence and level of antibodies against acetylcholine receptors (AChR Abs), treatments, thymic abnormalities. The primary outcome was the progression to GMG and/or the presence of bulbar symptoms. Secondary outcomes were either achievement of sustained minimal manifestation status or worsening in ocular quantitative MG subscore (O-QMGS) or worsening in total QMG score (T-QMGS), assessed by Myasthenia Gravis Foundation of America (MGFA) quantitative scores. Changes in mental and physical subscores of health-related quality of life (HRQoL) were assessed with SF-36 questionnaire. Variance analysis was used to interpret the differences between AChR Ab titers at different times of follow up among the generalized and non-generalized patients.

RESULTS

Conversion to GMG occurred in 18.4% of patients; it was significantly associated with sex, later onset of disease and anti-AChR Ab positivity. Antibody titer above the mean value of 25.8 pmol/mL showed no significant effect on generalization. Sex and late onset of disease significantly affected T-QMGS worsening. None of the other independent variables significantly affected O-QMGS and HRQoL.

CONCLUSIONS

Sex, later onset and anti-AChR Ab positivity were significantly associated with clinical worsening.

Methylome and transcriptome profiling in Myasthenia Gravis monozygotic twins

OBJECTIVE

To identify novel genetic and epigenetic factors associated with Myasthenia gravis (MG) using an identical twins experimental study design.

METHODS

The transcriptome and methylome of peripheral monocytes were compared between monozygotic (MZ) twins discordant and concordant for MG, as well as with MG singletons and healthy controls, all females. Sets of differentially expressed genes and differentially methylated CpGs were validated using RT-PCR for expression and target bisulfite sequencing for methylation on additional samples.

RESULTS

>100 differentially expressed genes and ∼1800 differentially methylated CpGs were detected in peripheral monocytes between MG patients and controls. Several transcripts associated with immune homeostasis and inflammation resolution were reduced in MG patients. Only a relatively few genes differed between the discordant healthy and MG co-twins, and both their expression and methylation profiles demonstrated very high similarity.

INTERPRETATION

This is the first study to characterize the DNA methylation profile in MG, and the expression profile of immune cells in MZ twins with MG. Results suggest that numerous small changes in gene expression or methylation might together contribute to disease. Impaired monocyte function in MG and decreased expression of genes associated with inflammation resolution could contribute to the chronicity of the disease. Findings may serve as potential new predictive biomarkers for disease and disease activity, as well as potential future targets for therapy development. The high similarity between the healthy and the MG discordant twins, suggests that a molecular signature might precede a clinical phenotype, and that genetic predisposition may have a stronger contribution to disease than previously assumed.

Effect of thymectomy for thymic atrophy in myasthenia gravis: A retrospective study on 93 patients

To clarify the efficacy of thymectomy among myasthenia gravis (MG) patients with and without thymoma. We classified MG patients who underwent thymectomy into 3 groups, such as thymic atrophy group, thymic follicular hyperplasia (TFH) group and thymoma group. We compared the data of clinical features and postoperative prognosis at very short-term, short-term, and medium-term. The clinical course of MG patients with atrophic thymus after thymectomy was even better than those of TFH or thymoma, in this retrospective study. However, we found no significant differences in the comparison of mean dose of prednisolone between the 3 groups at each time point.

Thymic pathologies in myasthenia gravis: a preoperative assessment of CAT scan and nuclear based imaging

Precise diagnostic work up of a suspected thymic pathology in patients with myasthenia gravis (MG) is very important for potential surgical implications and further disease course. In this study the diagnostic value of combined preoperative radiological (CAT scan) and nuclear based imaging (octreotide and thallium scintigraphy) in patients with MG was evaluated. Twenty four patients were included. Histopathology revealed thymoma in nine patients, thymic carcinoma (TC) in one patient, lymphofollicular hyperplasia in seven patients, and involuted thymus in another seven patients. Diagnostic sensitivity for detecting thymoma/TC was 80 % in CAT scan as well as in somatostatin scintigraphy; the combination of both procedures reached 90 %. However, the diagnostic specifity to exclude thymoma in CAT scan was 100 % and in octreotide scintigraphy 85.7 %. Semiquantitative octreotide uptake significantly correlated with histological grading of thymoma/TC (r = 0.764) and histological proliferation rate Ki67 (r = 0.894). Thallium scintigraphy was positive only in one out of four thymoma cases. In this study, somatostatin scintigraphy has been shown to be a useful additional diagnostic technique in detecting thymic malignancies in patients with MG. These results might be especially helpful in patients with late onset MG as these patients are in general no candidates for thymectomy.

Overcoming challenges in the diagnosis and treatment of myasthenia gravis

In recent years, the discovery of new autoantigens and the use of sensitive assays have expanded the clinical spectrum of myasthenia gravis (MG). In particular, antibodies binding to clustered acetylcholine receptors and to the low-density lipoprotein receptor-related protein 4 have not only bridged a significant gap in diagnosis but also have relevant clinical implications. MG management includes different therapeutic options, from symptomatic agents as the only therapy in mildly affected cases to combined long-term immunosuppression and thymectomy in patients with severe disabling disease. MG biological diversity can influence the response to therapies and should be taken into account when planning treatment. Biologic agents are promising, though their use is currently limited to patients with refractory disease.

Risk Factors and Outcomes in Cats with Acquired Myasthenia Gravis (2001-2012)

Background

Acquired myasthenia gravis (MG) in cats most commonly causes generalized weakness without megaesophagus and is more often associated with a cranial mediastinal mass, compared to dogs.

Hypothesis/Objectives

To extend the clinical findings described in the report of 2000 on MG in cats (J Am Vet Med Assoc 215:55–57).

Animals

Two hundred and thirty‐five cats with MG.

Methods

Retrospective case study to evaluate the long‐term outcome and incidence of spontaneous remission in myasthenic cats. Information including signalment, clinical presentation, presence of and type of cranial mediastinal mass, treatment including surgical versus medical, survival time, and outcome including spontaneous remissions was collected and analyzed in cats diagnosed at the Comparative Neuromuscular Laboratory, University of California San Diego by detection of acetylcholine receptor antibody titers >0.3 nmol/L by immunoprecipitation radioimmunosassay.

Results

Acquired MG in cats is associated with a euthanasia rate of 58%. Abyssinian and Somali cats had an increased incidence of MG compared to mixed breed cats or cats of other breeds. A cranial mediastinal mass, most commonly thymoma, was observed in 52% of the cats, which is higher than in the previous report. Spontaneous remission is not a characteristic of MG in cats.

Conclusions and clinical importance

Myasthenia gravis in cats is a chronic disease associated with a high incidence of a cranial mediastinal mass. Spontaneous remission is not common and clinicians should warn owners of the necessity for long‐term treatment. The clinical outcome with a cranial mediastinal mass did not differ between surgical or medical treatment.

Thymic lymphoid hyperplasia with multilocular thymic cysts diagnosed before the Sjögren syndrome diagnosis

Background

Thymic lymphoid hyperplasia is often present with myasthenia gravis as well as other autoimmune diseases such as systemic lupus erythematosus and rheumatoid arthritis. Of the 4 cases of thymic lymphoid hyperplasia associated with Sjögren syndrome that have been reported, no case with a thymic lesion diagnosis that led to the diagnosis of Sjögren syndrome has been reported. We herein report a case of thymic lymphoid hyperplasia with multilocular thymic cysts, diagnosed before Sjögren syndrome.

Case presentation

A 37-year-old Japanese woman had an approximate 5-cm anterior mediastinal mass detected by chest imaging. The resected lesion revealed multilocular thymic cysts that were filled with colloid-like material. Histology showed lymph follicular hyperplasia with many epithelial cysts. The epithelium consisted of thymic medullary epithelium, and no epithelial proliferation was seen in the lymphoid tissue. Lymphocytes were composed of an organized mixed population of mature T and B cells without significant atypia. The infiltrated B cells did not reveal light chain restriction or immunoglobulin heavy chain gene rearrangement. After the pathological diagnosis of thymic lesion, tests for the presence of autoantibodies were positive for antinuclear antibodies, rheumatic factor, and anti-SSA/Ro antibodies. The Schirmer’s, chewing gum, and Saxon tests showed decreased salivary and lacrimal secretion. Lip biopsy showed focal lymphocytic sialadenitis. The signs and symptoms of Sjögren syndrome had not resolved, without aggravation, 1 year after the thymectomy.

Conclusion

When a case with thymic lymphoid hyperplasia without myasthenia gravis is encountered, it is essential to consider the presence of another autoimmune disease including Sjögren syndrome.

Fusion protein of single-chain variable domain fragments for treatment of myasthenia gravis

Single-chain variable domain fragment (scFv) 637 is an antigen-specific scFv of myasthenia gravis. In this study, scFv and human serum albumin genes were conjugated and the fusion protein was expressed in Pichia pastoris. The affinity of scFv-human serum albumin fusion protein to bind to acetylcholine receptor at the neuromuscular junction of human intercostal muscles was detected by immunofluorescence staining. The ability of the fusion protein to block myasthenia gravis patient sera binding to acetylcholine receptors and its stability in healthy serum were measured by competitive ELISA. The results showed that the inhibition rate was 2.0-77.4%, and the stability of fusion protein in static healthy sera was about 3 days. This approach suggests the scFv-human serum albumin is a potential candidate for specific immunosuppressive therapy of myasthenia gravis.

The co-existence of myasthenia gravis in patients with myositis: a case series

OBJECTIVE

Myositis and myasthenia gravis (MG) are both autoimmune disorders presenting with muscle weakness. Rarely, they occur simultaneously in the same patient. Since the management of myasthenia gravis differs from that of myositis, it is important to recognize when patients have both diseases. We reviewed the cases of 6 patients with both myositis and MG to identify clinical features that suggest the possibility of co-existing MG in myositis patients.

METHODS

We identified 6 patients with dermatomyositis or polymyositis and MG. We reviewed their medical records to assess their clinical presentations, laboratory findings, and electrophysiological features.

RESULTS

All 6 patients had definite dermatomyositis or polymyositis by the criteria of Bohan and Peter as well as electrophysiologic and/or serologic confirmation of MG. Among overlap patients, 5/6 (83%) had bulbar weakness, 2/6 (33%) had ptosis, and 1/6 (17%) had diplopia. Fatigable weakness was noted by 5/6 (83%) patients. Treatment with pyridostigmine improved symptoms in 5/6 (83%) patients. High-dose steroids were associated with worsening weakness in 2/6 (33%) patients.

CONCLUSIONS

Prominent bulbar symptoms, ptosis, diplopia, and fatigable weakness should suggest the possibility of MG in patients with myositis. A suspicion of MG may be confirmed through appropriate electrophysiologic and laboratory testing. In those with myositis-MG overlap, high-dose steroids may exacerbate symptoms and pyridostigmine may play an important therapeutic role.