Myasthenia gravis and thymic neoplasms: A brief review

Rechallenge of immune checkpoint inhibitors in a case with adverse events inducing myasthenia gravis

The mechanism(s) of immune checkpoint inhibitor (ICI)-induced myasthenia gravis (MG), an immune-related adverse event (irAE) that is fatal and limits subsequent ICI use, remain unexplored. Here, through comparative genomic analysis, we identified a pathogenic p.S467C germline variant in SLC22A5 in a thymoma case with ICI-induced MG, which was found to be associated with fatty acid oxidation through its regulation on L-carnitine levels. Remarkably, ICI rechallenge with L-carnitine pretreatment led to durable response without MG-related symptoms. Thus, we provide the first clinical evidence of genetic test-directed irAE management, which integrates individualized ICI treatment into the evolving paradigm of cancer management.

A case of uniportal VATS thymectomy for Thymoma associated with myasthenia gravis and toxic multinodular goiter

BACKGROUND

Thymoma is a rare neoplasm, which may be associated with autoimmune disorders, the occurrence of hyperthyroidism in the patients with thymoma is rare.

CLINICAL PRESENTATION

Here we present an extremely rare case of a 56-year-old female patient who was discovered to have malignant thymoma with associated myasthenia gravis and hyperthyroidism due to toxic multinodular goiter. Our patient started to complain of difficulty breathing and swallowing, Chest CT scan was done and revealed an anterior mediastinal mass, measures about 4.1 × 3.1 × 2.2 cm with enlarged lymph node mostly representing thymoma. Complete thymectomy was performed via uniportal video-assisted thoracoscopic surgery, and the patient's postoperative recovery was uneventful. Microscopic histopathology findings corresponded to thymoma type B1.

CONCLUSION

The coexistence of thymoma, MG and toxic multinodular goiter is extremely rare. MG should always be suspected in a patient with thymoma. VATS thymectomy has been increasingly used to treat thymoma as it has several advantages over open surgery.

Novel treatment strategies for acetylcholine receptor antibody-positive myasthenia gravis and related disorders

The presence of autoantibodies directed against the muscle nicotinic acetylcholine receptor (AChR) is the most common cause of myasthenia gravis (MG). These antibodies damage the postsynaptic membrane of the neuromuscular junction and cause muscle weakness by depleting AChRs and thus impairing synaptic transmission. As one of the best-characterized antibody-mediated autoimmune diseases, AChR-MG has often served as a reference model for other autoimmune disorders. Classical pharmacological treatments, including broad-spectrum immunosuppressive drugs, are effective in many patients. However, complete remission cannot be achieved in all patients, and 10% of patients do not respond to currently used therapies. This may be attributed to production of autoantibodies by long-lived plasma cells which are resistant to conventional immunosuppressive drugs. Hence, novel therapies specifically targeting plasma cells might be a suitable therapeutic approach for selected patients. Additionally, in order to reduce side effects of broad-spectrum immunosuppression, targeted immunotherapies and symptomatic treatments will be required. This review presents established therapies as well as novel therapeutic approaches for MG and related conditions, with a focus on AChR-MG.

Immune-Related Molecular Profiling of Thymoma With Myasthenia Gravis

Background: Approximately 50% of thymoma patients also show myasthenia gravis (MG), which is an autoimmune disease; however, the pathogenesis of MG-associated thymoma remains elusive. Our aim was to investigate immune-related lncRNA profiles of a set of candidate genes for better understanding of the molecular mechanism underlying the pathogenesis of thymoma with or without MG. Methods: Molecular profiles of thymoma with or without MG were downloaded from The Cancer Genome Atlas, and Pearson's correlation analysis was performed to identify immune-related lncRNAs. T test was used to examine the differential expression and differential methylation between thymoma patients with or without MG. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analyses were performed to predict the function of target genes of immune-related lncRNAs. Results: Analyses of the 87 thymoma samples with complete MG information revealed that 205 mRNAs and 56 lncRNAs showed up-regulated expression in thymoma with MG patients, while 458 mRNAs and 84 lncRNAs showed down-regulated expression. The methylation level of three immune-related lncRNAs (AP000787.1, AC004943.1, WT1-AS, FOXG1-AS1) was significantly decreased in thymoma tissues, and the methylation level of these immune-related lncRNAs (WT1-AS: Cor = 0.368, p < 0.001; FOXG1-AS1: Cor = 0.288, p < 0.01; AC004943.1: Cor = -0.236, p < 0.05) correlated with their expression. GO and KEGG pathway analysis revealed that targets of the immune-related lncRNA FOXG1-AS1 were enriched in small GTPase binding and herpes simplex virus 1 infection. Transcription coregulator activity and cell cycle were the most enriched pathways for targets of lncRNA AC004943.1. LncRNA WT1-AS targets were most enriched in actin binding and axon guidance. Conclusion: Our results revealed the immune-related molecular profiling of thymoma with MG and without MG and identified key pathways involved in the underlying molecular mechanism of thymoma-related MG. These findings provide insights for further research of potential markers for thymoma-related MG.

Robotic thymectomy for thymomas: a retrospective follow-up study in the Netherlands

BACKGROUND

The Maastricht University Medical Center+ (MUMC+) is a Dutch center of expertise, appointed by the Netherlands Federation of University Medical Centres (NFU), for the treatment of thymomas. The aim of this study was to investigate the long-term oncological-, surgical-, and neurological outcomes of all patients who underwent a robotic thymectomy for a thymoma at the MUMC+.

METHODS

We retrospectively analyzed the clinical-pathological data of all consecutive patients with a thymoma who underwent robotic thymectomy using the DaVinci® Robotic System at the MUMC+ between April 2004 and December 2018. Follow-up data were collected from 60 referring Dutch hospitals.

RESULTS

In total, 398 robotic thymectomies were performed and 130 thymomas (32.7%) were found. Median follow-up time, procedure time and hospitalization were 46 months, 116 minutes and 3 days, respectively. In 8.4% of the patients a conversion was performed and in 20.8% a complication was registered. The majority of myasthenic patients with a thymoma went into remission, mostly within 12 to 24 months after thymectomy (81.0%). No statistical difference was found in the number of complications, conversions, incomplete resections or deaths between patients with myasthenia gravis and nonmyasthenic patients. Thirty-six patients (27.7%) underwent postoperative radiotherapy. The recurrence rate was 9.1% and the five-year thymoma-related survival rate was 96.6% .

CONCLUSIONS

Robotic thymectomy was found to be safe and feasible in early-stage thymomas, most advanced-stage thymomas and thymomatous myasthenia gravis. A national guideline could contribute to the improvement of the oncological follow-up of thymic epithelial tumors in the Netherlands.

Sphingomonas and Phenylobacterium as Major Microbiota in Thymic Epithelial Tumors

The microbiota has been reported to be closely associated with carcinogenesis and cancer progression. However, its involvement in the pathology of thymoma remains unknown. In this study, we aimed to identify thymoma-specific microbiota using resected thymoma samples. Nineteen thymoma tissue samples were analyzed through polymerase chain reaction amplification and 16S rRNA gene sequencing. The subjects were grouped according to histology, driver mutation status in the GTF2I gene, PD-L1 status, and smoking habits. To identify the taxa composition of each sample, the operational taxonomic units (OTUs) were classified on the effective tags with 97% identity. The Shannon Index of the 97% identity OTUs was calculated to evaluate the alpha diversity. The linear discriminant analysis effect size (LEfSe) method was used to compare the relative abundances of all the bacterial taxa. We identified 107 OTUs in the tumor tissues, which were classified into 26 genera. Sphingomonas and Phenylobacterium were identified as abundant genera in almost all the samples. No significant difference was determined in the alpha diversity within these groups; however, type A thymoma tended to exhibit a higher bacterial diversity than type B thymoma. Through the LEfSe analysis, we identified the following differentially abundant taxa: Bacilli, Firmicutes, and Lactobacillales in type A thymoma; Proteobacteria in type B thymoma; Gammaproteobacteria in tumors harboring the GTF2I mutation; and Alphaproteobacteria in tumors without the GTF2I mutation. In conclusion, Sphingomonas and Phenylobacterium were identified as dominant genera in thymic epithelial tumors. These genera appear to comprise the thymoma-specific microbiota.

Acetylcholinesterase and human cancers

The enzyme acetylcholinesterase (AChE) is a serine hydrolase whose primary function is to degrade acetylcholine (ACh) and terminate neurotransmission. Apart from its role in synaptic transmission, AChE has several "non-classical" functions in non-neuronal cells. AChE is involved in cellular growth, apoptosis, drug resistance pathways, response to stress signals and inflammation. The observation that the functional activity of AChE is altered in human tumors (relative to adjacent matched normal tissue) has raised several intriguing questions about its role in the pathophysiology of human cancers. Published reports show that AChE is a vital regulator of oncogenic signaling pathways involving proliferation, differentiation, cell-cell adhesion, migration, invasion and metastasis of primary tumors. The objective of this book chapter is to provide a comprehensive overview of the contributions of the AChE-signaling pathway in the growth of progression of human cancers. The AChE isoforms, AChE-T, AChE-R and AChE-S are robustly expressed in human cancer cell lines as well in human tumors (isolated from patients). Traditionally, AChE-modulators have been used in the clinic for treatment of neurodegenerative disorders. Emerging studies reveal that these drugs could be repurposed for the treatment of human cancers. The discovery of potent, selective AChE ligands will provide new knowledge about AChE-regulatory pathways in human cancers and foster the hope of novel therapies for this disease.

Risk of malignancies in patients with inflammatory bowel disease who used thiopurines as compared with other indications: a territory-wide study

AIMS

Thiopurines are believed to increase cancer risks, but data from Asian patients are sparse. We determined the risks of malignancies in thiopurine users with inflammatory bowel disease (IBD) or other indications from Hong Kong.

METHODS

All patients who had received thiopurines between 2005 and 2009 in Hong Kong were identified from local electronic healthcare database. Patients were followed from the start date of thiopurines until death or end of study in 2017. We excluded patients with baseline malignancy. Standardized incidence ratios (SIR) and the corresponding 95% confidence intervals (CI) of all malignancies were computed against matched local general population from the cancer registry. Patients in the same diagnosis category but not exposed to thiopurines were included as controls.

RESULTS

There were 7452 thiopurines users (median age 47.0 years), including 595 IBD patients, with a median follow-up of 11.2 years. Of them, 684 (9.2%) developed malignancies with an overall SIR of 2.30 (95% CI 2.13-2.48). The SIR in IBD patients who used thiopurines was 2.37 (95% CI 1.71-3.18) as compared with non-users (SIR 1.35, 95% CI 1.05-1.72). Highest risk of malignancies was observed in post-transplant patients (SIR 3.83, 95% CI 3.34-4.35), and lower risks were seen in patients with rheumatological diseases (SIR 1.46, 95% CI 1.02-2.02).

CONCLUSION

IBD patients in Hong Kong who used thiopurines had 2.37-fold increase in risk of malignancies than the general population, which was higher than non-users and different from thiopurine users for other indications.

Neurologic Symptoms Caused by Mature Cystic Teratoma of the Thymus

This case report describes an unusual presentation of a rare mature cystic teratoma of the thymus. It was indistinguishable from other anterior mediastinal masses without surgical resection and histologic diagnosis. Malignant thymic masses and mediastinal masses that cause compression of the heart and surrounding vessels have been reported to cause paresthesia. However, this case documents a mediastinal teratoma, specifically a benign thymic teratoma, that presented with symptoms of sensory dysfunction among other neurologic deficits. Complete surgical resection of the teratoma was performed without complications, and all symptoms resolved.

Evidence-Based Practice in Rehabilitation of Myasthenia Gravis. A Systematic Review of the Literature

Myasthenia gravis is a rare neuromuscular disorder characterized by muscle weakness and fatigue. This review analyzes the most recent evidence regarding the effectiveness and safety of different rehabilitative approaches to the disease. The review was carried out in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. A total of 365 articles were found in the main scientific databases. Applying the inclusion/exclusion criteria, 11 studies were admitted to the final phase of the review. Three different rehabilitative approaches were identified: physical training, respiratory training, and balance training. All rehabilitative modalities contributed to enhancing functional outcomes, reducing fatigue, and improving quality of life, but currently none can be recommended over another for the lack of cross-comparative studies. The included studies showed methodological quality from low to fair. Despite the range of rehabilitative interventions available, there is a lack of high-quality evidence. However, this review suggests that a multidisciplinary rehabilitation approach should be recommended to people with myasthenia gravis, and above all, for those with mild to moderate symptomatology.

Unraveling the Role of Receptor for Advanced Glycation End Products (RAGE) and Its Ligands in Myasthenia Gravis

Myasthenia gravis (MG) is an autoimmune T cell-dependent B cell-mediated disorder of the neuromuscular junction (NMJ) characterized by fluctuating skeletal muscle weakness, most commonly attributed to pathogenic autoantibodies against postsynaptic nicotinic acetylcholine receptors (AChRs). Although MG pathogenesis is well-documented, there are no objective biomarkers that could effectively correlate with disease severity or MG clinical subtypes, and current treatment approaches are often ineffective. The receptor for advanced glycation end products (RAGE) is a multiligand cell-bound receptor highly implicated in proinflammatory responses and autoimmunity. Preclinical evidence demonstrates that RAGE and its ligand S100B are upregulated in rat models of experimental autoimmune myasthenia gravis (EAMG). S100B-mediated RAGE activation has been shown to exacerbate EAMG, by enhancing T cell proinflammatory responses, aggravating T helper (Th) subset imbalance, increasing AChR-specific T cell proliferative capacity, and promoting the production of antibodies against AChRs from the spleen. Soluble sRAGE and esRAGE, acting as decoys of RAGE ligands, are found to be significantly reduced in MG patients. Moreover, MG has been associated with increased serum levels of S100A12, S100B and HMGB1. Several studies have shown that the presence of thymic abnormalities, the onset age of MG, and the duration of the disease may affect the levels of these proteins in MG patients. Herein, we discuss the emerging role of RAGE and its ligands in MG immunopathogenesis, their clinical significance as promising biomarkers, as well as the potential therapeutic implications of targeting RAGE signaling in MG treatment.

Persistent type 2 respiratory failure on background of advanced thymoma with lung metastases

We report a patient in her 60s with history of end-stage thymoma with bilateral lung metastases on palliative chemotherapy presented to the hospital with sudden shortness of breath initially treated for probable pulmonary embolism (PE) pending CT of the pulmonary arteries which was subsequently negative for PE. During this admission, she developed transient right-sided facial droop and slurred speech which resolved spontaneously; however, the patient became unresponsive and desaturated with severe decompensated type 2 respiratory failure. Patient was supported with non-invasive ventilation (biphasic positive airway pressure) for few days. Myasthenia gravis was suspected due to clinical features and confirmed by the high titre of acetylcholine receptor antibody titre.

Molecular profiling of thymoma with myasthenia gravis: Risk factors of developing myasthenia gravis in thymoma patients

OBJECTIVE

Thymoma is a rare epithelial tumor arising from the thymus in the anterior mediastinum. Nearly 50% of patients with thymoma develop myasthenia gravis, which is an indication of a poor long-term prognosis. Here, we identified specific and effective molecular markers for predicting in the development of myasthenia gravis patients with thymoma.

MATERIAL AND METHODS

We investigated molecular profiling based on RNA-sequencing (RNA-seq) for myasthenia gravis development in patients with thymoma. RNA was extracted from 34 patients with thymoma, 16 of whom had myasthenic and 18 of whom did not, and transcriptome profiles were analyzed through next-generation sequencing.

RESULTS

We discovered 140 differential expressed genes associated with myasthenia gravis in thymoma patients. The four genes, hypoxia-inducible factor 3 alpha (HIF3A), insulin-like growth factor-binding protein 1, pyruvate dehydrogenase kinase, and Krüppel-like factor 15 were differentially expressed in patients with thymoma who has myasthenia gravis and were validated by quantitative polymerase chain reaction. HIF3A expression was significantly higher in patients with myasthenia gravis than in those without.

CONCLUSION

HIF3A is aberrantly expressed in patient with thymoma who has myasthenia gravis and may be involved in the development of myasthenia gravis in thymoma patient.

Results of Robotic Thymectomy Performed in Myasthenia Gravis Patients Older Than 60 Years at Onset

BACKGROUND

Data are limited on the safety and efficacy of robotic thymectomy in patients with myasthenia gravis (MG) older than 60 years at onset.

METHODS

Patients older than 60 years at MG onset who underwent robotic thymectomy in Charite Universitaetsmedizin Berlin between 2003 and 2017 were potentially eligible for inclusion. The main outcomes were perioperative complications and clinical outcome according to the Myasthenia Gravis Foundation of America Post-Intervention Status.

RESULTS

Sixty-eight (25 women, 43 men) of 580 patients with MG who underwent robotic thymectomy were eligible for perioperative analyses (median age at MG onset 67 years, range: 61 to 85 years). The perioperative morbidity rate was 13.2%, and the only perioperative death was due to aortic dissection. Fifty-one patients were available for further analysis with a median follow-up time of 60 months (range: 12 to 263 months). The complete stable remission rate was 7.8%, the improvement rate was 68.6%, and the overall mortality rate was 11.8%. Compared with preoperative use, the mean daily dose of corticosteroid agents was significantly reduced at the last follow-up (17.6 ± 23.6 mg versus 2.6 ± 6.1 mg, p = 0.0001) without increased use of azathioprine (35.9 ± 61.9 mg versus 42.7 ± 59 mg, p = 0.427). After excluding 2 patients seronegative for the anti-acetylcholine receptor antibody, 10 of 49 seropositive patients achieved "good outcome" (including four complete stable remissions, three pharmacologic remissions, and three minimal manifestations 0) which was predicted by being free of concomitant disease (odds ratio 7.307, 95% confidence interval: 1.188 to 44.937, p = 0.032) and Myasthenia Gravis Foundation of America classification I before thymectomy (odds ratio 6.696, 95% confidence interval: 1.259 to 35.620, p = 0.026).

CONCLUSIONS

Robotic thymectomy seems to be safe and effective in patients with MG older than 60 years at onset with a statistically significant steroid-sparing effect.

Myasthenia gravis as a prognostic marker in patients with thymoma

Background

Thymoma is the most common mediastinal tumor, representing <1% of all cancers. It is usually associated with paraneoplastic disorders, mainly myasthenia gravis (MG). The aim of the present study was to describe patients with thymoma and the differences between those with MG and those without it.

Methods

A retrospective 10-year database of the patients with thymoma treated at a single cancer referral hospital (National Institute of Cancer, Mexico City), was analyzed.

Results

Sixty-four files from patients with thymoma were analyzed, 18 of them had MG. The symptoms that occurred most frequently in patients with MG were ptosis, diplopia, appendicular weakness, dysphonia and dysphagia. The most frequent Myasthenia Gravis Foundation of America (MGFA) stage was IIIb followed by stage I. Almost all the patients with MG had positive Acetylcholine Receptor antibodies (P<0.001), with not specified antibodies in four patients. The median overall survival showed a trend to be higher among the patients with MG, but there were no significant differences.

Conclusions

In patients with thymoma MG manifests with different clinical and autoimmune traits, but not survival differences. A larger multi-centric study should be encouraged to evaluate the prognostic implications of having MG in patients with thymoma.

Robotic versus thoracoscopic thymectomy: The current evidence

BACKGROUND

The purpose of this study was to analyze all relevant comparative studies comparing robot-assisted minimally invasive thymectomy (RATS) and video-assisted thoracic surgery thymectomy (VATS) in terms of surgical and short-term outcomes.

METHODS

A systematic search for articles describing robot-assisted and video-assisted thymectomy and addressing surgical outcomes, operation time, length of hospitalization, intra-operative blood loss, conversion to sternotomy and post-operative complications was performed using the medical databases.

RESULTS

Of the 478 studies from preliminary screening, five articles were included. By pooling these studies, we found no significant differences between the RATS and VATS (odds ratio 1.24 (95% CI 0.51, 3.03; p = 0.63)).There were no significant differences in comparison of conversion rates, operation time (26.29 min (95% CI -2.57, 55.35; p = 0.07)) and length of hospitalization (-1.58 days (95% CI -4.78, 1.62; p = 0.33)). There was a slightly higher blood loss in the RATS group.

CONCLUSION

Our meta-analysis did not detect any statistically significant differences in surgery outcomes between the two groups.

Thymectomy in Myasthenia Gravis

In recent years, thymectomy has become a widespread procedure in the treatment of myasthenia gravis (MG). Likelihood of remission was highest in preoperative mild disease classification (Osserman classification 1, 2A). In absence of thymoma or hyperplasia, there was no relationship between age and gender in remission with thymectomy. In MG treatment, randomized trials that compare conservative treatment with thymectomy have started, recently. As with non-randomized trials, remission with thymectomy in MG treatment was better than conservative treatment with only medication. There are four major methods for the surgical approach: transcervical, minimally invasive, transsternal, and combined transcervical transsternal thymectomy. Transsternal approach with thymectomy is the accepted standard surgical approach for many years. In recent years, the incidence of thymectomy has been increasing with minimally invasive techniques using thoracoscopic and robotic methods. There are not any randomized, controlled studies which are comparing surgical techniques. However, when comparing non-randomized trials, it is seen that minimally invasive thymectomy approaches give similar results to more aggressive approaches.