A tale of autoimmunity: thymoma, thymectomy, and systemic lupus erythematosus

Single-Cell Transcriptomics Identifies a Prominent Role for the MIF-CD74 Axis in Myasthenia Gravis Thymus

BACKGROUND AND OBJECTIVES

Myasthenia gravis (MG) is an autoimmune disease most frequently caused by autoantibodies (auto-Abs) against the acetylcholine receptor (AChR) located at the neuromuscular junction. Thymic follicular hyperplasia is present in most of the patients with early-onset AChR-Ab+ MG (EOMG), but its cellular and molecular drivers and development remain poorly understood.

METHODS

We constructed a single cell-based transcriptional profile of lymphoid cell types in thymi from 11 immunotherapy-naïve patients with EOMG. Multiplex histology and ELISA were used to determine migration inhibitory factor (MIF) levels.

RESULTS

Within EOMG thymi, we consistently observed 6 distinct clusters of B-cell populations maturing toward germinal center (GC)-associated and Ab-secreting cells, featuring prominent GC activity, as indicated by substantial clonal expansions and cycling B-cell subsets. Cell-cell interactome predictions identified strong interactions between T cells and GC-associated and memory B cells, dominated by B-cell prosurvival signaling through the MIF-CD74 axis. Multiplex histology confirmed abundant expression of CD74 in MG thymic B cells. Circulating MIF levels in EOMG correlated with higher disease severity as assessed by Myasthenia Gravis Foundation of America status.

DISCUSSION

Our data not only illustrate and define hyperplastic thymic niches in MG as favorable environments for pathogenic B-cell proliferation, maturation, and persistence but also suggest that the MIF-CD74 axis should be investigated for potential novel therapeutic targeting in EOMG.

Paraneoplastic systemic lupus erythematosus associated with dysgerminoma: a case report and literature review

Rheumatic paraneoplastic syndromes are rare and generally occur no longer than two years before diagnosis of the associated malignancy. Therefore, it can be an essential clue to occult malignancy. A healthy 18-year-old female with no underlying diseases was referred to the rheumatology clinic due to morning stiffness in her hands and a new rash on her fingers. Her labs showed a positive ANA, anti-double strand DNA antibody, anti-RNP, and anti-ribosomal P. Nine months after the diagnosis with SLE, the patient presented with elevated levels of lactate dehydrogenase. A total-body computed tomography scan revealed a solid mass in the pelvis. The pathological findings corresponded to a dysgerminoma tumor. Following surgical tumor removal and chemotherapy, the patient went into remission with both SLE and her oncology conditions, with no relapse of her lupus symptoms in a one-year follow-up. This case underscores the importance of considering malignancy in unexplained lupus symptoms, a crucial point for all physicians to be aware of. We identified 13 cases of paraneoplastic SLE in a literature review. In most cases, SLE is resolved after the tumor has been treated.

Rapid growing mass of the mandible due to an oral metastasis of thymoma: Case report of an extremely rare localization and review of published cases

Background

Cancer metastases in the oral cavity are relatively uncommon, occurring in approximately 1-3% of malignant cases. Thymomas and thymic carcinomas are the two main tumors that can affect the thymus, a lymphatic gland that plays an important role in regulating the immune system. The aims of this paper are (i) to describe an extremely rare case of thymoma metastasis to the oral cavity (ii) report all published cases of thymic tumor metastases to the oral cavity.

Case report

A 62-year-old Italian male patient was referred to the Oral Medicine Department at the Fondazione Policlinico Universitario A. Gemelli - IRCCS, Rome to evaluate a rapidly growing, non-ulcerated swelling in the left buccal mucosa. After clinical examination and radiological examination, an incisional biopsy was performed under local anesthesia. Thus, a final diagnosis of intraoral metastasis of thymoma was achieve.A review of the literature of oral metastases due to thymic tumor was also conducted through a systematic search in accordance with PRISMA guidelines, via PubMed, Scopus and CENTRAL engines. Out of 328 articles retrieved, only two articles reported oral metastasis of thymic tumors; and two reports of ectopic thymic carcinoma of the parotid gland were found.

Conclusions

This paper provides a rare case of oral metastasis of thymoma. The present paper reports an almost undescribed condition. Future reports will be useful in increasing knowledge regarding this area. The oral screening of patients with thymic tumors could be useful, considering the relationship between these diseases and oral disorders.

Unique association of anti-GABAA receptor encephalitis and myasthenia gravis in a patient with type A thymoma

Association between anti-GABAAR encephalitis and myasthenia gravis is extremely rare with few reported cases. Herein, we report a case of a female patient diagnosed with anti-GABAAR encephalitis and thymoma at the first admission. She was administered glucocorticoids for long-term immunotherapy, and thymectomy with biopsy demonstrated a type A thymoma. After 4 months, the symptoms of encephalitis were relieved, but she then developed post-thymectomy myasthenia gravis with anti-AChR and anti-titin dual positivity. Antibodies to connective tissue (anti-ANA, anti-PCNA) and those characteristics of paraneoplastic syndrome (anti-Ma2/Ta) were also positive. She received oral glucocorticoids and tacrolimus as immunosuppressive therapy, and myasthenic symptoms were stable during a 2-year follow-up. Our case revealed that anti-GABAAR encephalitis and myasthenia gravis can appear in patient with type A thymoma at different periods, which alerts physicians to take long-term follow-up for anti-GABAAR encephalitis with thymoma, even after thymectomy. Concurrent positivity for more than one antibody after thymectomy is rarely observed, and their contribution to the clinical course and treatment decision remains to be further investigated.

Immune tolerance and the prevention of autoimmune diseases essentially depend on thymic tissue homeostasis

The intricate balance of immune reactions towards invading pathogens and immune tolerance towards self is pivotal in preventing autoimmune diseases, with the thymus playing a central role in establishing and maintaining this equilibrium. The induction of central immune tolerance in the thymus involves the elimination of self-reactive T cells, a mechanism essential for averting autoimmunity. Disruption of the thymic T cell selection mechanisms can lead to the development of autoimmune diseases. In the dynamic microenvironment of the thymus, T cell migration and interactions with thymic stromal cells are critical for the selection processes that ensure self-tolerance. Thymic epithelial cells are particularly significant in this context, presenting self-antigens and inducing the negative selection of autoreactive T cells. Further, the synergistic roles of thymic fibroblasts, B cells, and dendritic cells in antigen presentation, selection and the development of regulatory T cells are pivotal in maintaining immune responses tightly regulated. This review article collates these insights, offering a comprehensive examination of the multifaceted role of thymic tissue homeostasis in the establishment of immune tolerance and its implications in the prevention of autoimmune diseases. Additionally, the developmental pathways of the thymus are explored, highlighting how genetic aberrations can disrupt thymic architecture and function, leading to autoimmune conditions. The impact of infections on immune tolerance is another critical area, with pathogens potentially triggering autoimmunity by altering thymic homeostasis. Overall, this review underscores the integral role of thymic tissue homeostasis in the prevention of autoimmune diseases, discussing insights into potential therapeutic strategies and examining putative avenues for future research on developing thymic-based therapies in treating and preventing autoimmune conditions.

Sudden Death Due to Coronary Vasculitis: An Unexpected Autopsy Finding and Unusual Association With Thymic Hyperplasia

A 43-year-old Asian woman was found unresponsive on the sidewalk, prompting a call to 911. Upon transportation to the hospital, no signs of trauma were evident, but her condition deteriorated, leading to her eventual passing. An autopsy revealed a complete occlusion of the right coronary artery due to segmental coronary artery vasculitis. Without details of the individual's social or medical history, the specific type of coronary vasculitis couldn't be determined. The internal examination also showed thymic hyperplasia of unknown origin. While there is no conclusive evidence, a potential link between thymic hyperplasia, immune dysregulation, and coronary artery vasculitis is discussed, considering the case and existing literature.

Anti-dsDNA Is Associated with Favorable Prognosis in Myasthenia Gravis: A Retrospective Study

Objectives. To investigate the presence of serum antinuclear antibody (ANA) and anti-double-stranded DNA antibody (anti-dsDNA) in patients with myasthenia gravis (MG) and analyze the clinical characteristics and prognostic factors associated with MG. Methods. We retrospectively enrolled 363 patients with MG and analyzed the clinical characteristics and follow-up data between patients positive and negative for ANA and anti-dsDNA. We defined a Myasthenia Gravis Activities of Daily Living (MG-ADL) reduction as a main prognosis predictor and used logistic regression to determine independent factors associated with prognosis. We built a nomogram to predict prognosis and evaluate the internal validity of the model. Results. Ninety-eight (27.0%) patients were positive for ANA, and 51 (14.0%) were positive for anti-dsDNA. Patients positive for ANA and anti-dsDNA antibodies tended to be female and positive for acetylcholine receptor antibody (AChR-Ab). The rate of thymoma was higher in anti-dsDNA-positive patients with MG (p-dsDNA-MG) than in patients negative for anti-dsDNA (49.0% vs. 26.0%, $p=0.001$ ), and p-dsDNA-MG was associated with reduced MG-ADL score. Regression analysis showed that except for age of onset ( $\text{OR}=0.986$ , $95\%\text{CI}=0.973–0.999$ , $p=0.037$ ), anti-dsDNA ( $\text{OR}=2.800$ , $95\%\text{CI}=1.381–5.679$ , $p=0.004$ ), ptosis ( $\text{OR}=2.930$ , $95\%\text{CI}=1.827–4.699$ , $p<0.001$ ), and eye movement disorder ( $\text{OR}=2.815$ , $95\%\text{CI}=1.672–4.741$ , $p<0.001$ ) were independent predictive factors of a favorable prognosis of MG. These predictors were used to generate a nomogram with an excellent predictive value. Conclusions. Being female and the presence of AChR-Ab were features of ANA- or anti-dsDNA-positive MG. The presence of anti-dsDNA was associated with a favorable prognosis of MG.

Concurrent de novo Thymoma-associated Paraneoplastic Type 1 Autoimmune Hepatitis and Pure Red Cell Aplasia after Thymectomy: A Case Report and Literature Review

The precise manipulation of immune tolerance is the holy grail of immunotherapies for both autoimmunity and cancer immunity. Thymomas are well known to be associated with autoimmune diseases. The exact mechanism by which autoreactivity is induced after thymectomy remains to be elucidated. We herein present the case of a 50-year-old lady with concurrent de novo type 1 autoimmune hepatitis (AIH) and pure red cell aplasia (PRCA), 1 month after undergoing a successful total thymectomy for combined squamous cell carcinoma and thymoma (Masaoka stage II). Corticosteroids yielded short-term effects for both AIH and PRCA. Literature on thymoma-associated AIH, an extremely rare immune-related comorbidity, was also reviewed.

Two Very Rare Cases of Metastatic Thymic Carcinoma with Sjogren's Syndrome: A Case Series

Thymic tumours are rare thoracic malignancies with thymic carcinoma accounting for approximately 12% of all thymic tumours compared to thymomas which account for approximately 86%. Unlike thymomas, it is very rare for thymic carcinomas to be associated with autoimmune disorders or paraneoplastic syndromes. When these phenomena do occur, the vast majority are myasthenia gravis, pure red cell aplasia, or systemic lupus erythematous. Paraneoplastic Sjogren's syndrome is a rare complication of thymic carcinoma, with only two cases previously reported. Here we present 2 cases of patients with metastatic thymic carcinoma who developed autoimmune phenomena consistent with Sjogren's syndrome without classical symptoms prior to treatment. One patient opted for surveillance of their malignancy, while the other underwent chemoimmunotherapy with favourable results. These case reports describe two distinctive clinical presentations of a rare paraneoplastic phenomenon.

Regulation of thymic T regulatory cell differentiation by TECs in health and disease

The thymus produces self-limiting and self-tolerant T cells through the interaction between thymocytes and thymus epithelial cells (TECs), thereby generating central immune tolerance. The TECs are composed of cortical and medullary thymic epithelial cells, which regulate the positive and negative selection of T cells, respectively. During the process of negative selection, thymocytes with self-reactive ability are deleted or differentiated into regulatory T cells (Tregs). Tregs are a subset of suppressor T cells that are important for maintaining immune homeostasis. The differentiation and development of Tregs depend on the development of TECs and other underlying molecular mechanisms. Tregs regulated by thymic epithelial cells are closely related to human health and are significant in autoimmune diseases, thymoma and pregnancy. In this review, we summarize the current molecular and transcriptional regulatory mechanisms by which TECs affect the development and function of thymic Tregs. We also review the pathophysiological models of thymic epithelial cells regulating thymic Tregs in human diseases and specific physiological conditions.

LncRNA and mRNA expression associated with myasthenia gravis in patients with thymoma

Objective

Pathological alterations of the thymus are observed in the majority of patients with myasthenia gravis (MG). To explore the potential mechanisms of these alterations, we performed a transcriptome analysis and measured co‐expression of aberrant long non‐coding RNAs (lncRNAs) and messenger RNAs (mRNAs).

Methods

RNA was extracted from eight patients with thymoma, five of whom had MG. Transcriptome profiles were acquired through mRNA and lncRNA microarray analysis. Quantitative reverse transcription polymerase chain reaction was used to verify the results of the microarray analysis. LncRNAs co‐expressed with mRNA were analyzed with Pearson's coefficient. Next, cis‐regulated and trans‐regulated target genes were predicted. The functions of aberrant lncRNAs were explored on the basis of Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses of target mRNAs.

Results

The comparative microarray analysis identified 4360 lncRNAs and 2545 mRNAs with significant differential expression. The most significant GO enrichment terms were phosphoric ester hydrolase activity, phosphatase activity, and hydrolase activity, which were assigned as molecular functions. Regulation of endosome size was the most significant GO enrichment term assigned as a biological process, and Golgi apparatus was the most significant GO enrichment term assigned as cellular component. The reliability prediction terms of KEGG included calcium signaling pathway, glycosphingolipid biosynthesis, and caffeine metabolism.

Conclusion

MG‐positive thymoma is associated with overactive biological processes and molecular functions, especially dephosphorylation and hydrolysis, which may affect thymocyte survival during selection in the thymus.

Viral infection in thymoma and thymic tumors with autoimmune diseases

A thymoma is a type of thymic tumor which is rarely malignant that is frequently reported in adult patients. A number of thymoma-related immune disorders are observed including autoimmune diseases, which suggests a strong connection between thymoma development and immunological mechanisms. Characterized by association with humoral and cellular immunodeficiency, thymoma patients are susceptible to opportunistic infections by environmental factors. Recent reports have suggested that viral infection may play a role in the etiological mechanisms of thymoma development associated with dysregulated immunity. In this review, we summarize the case reports and studies related to viral infection, such as CMV, EBV and HSV, that probably play a part in the pathogenesis of thymoma and related diseases. Furthermore, we demonstrate the underlying mechanisms by which viruses may induce the occurrence of thymoma with autoimmune diseases. Lastly, we discuss the potential application of antiviral therapy in the treatment of thymic diseases.

Mixed connective tissue disease after thymectomy in refractory myasthenia gravis

Connective tissue diseases, including systemic lupus erythematosus (SLE) and systemic sclerosis are classic models of autoimmunity; diseases with large-scale loss of tolerance and subsequent development of pathogenic autoreactive lymphocytes and tissue targeting autoantibodies. Here we report a case of mixed connective tissue disease, with features of systemic lupus erythematosus and systemic sclerosis developing in a patient 10 years post thymectomy for myasthenia gravis. The patient developed acute cutaneous lupus, Raynaud's with digital ulcers, arthritis and lymphopenia. Her myasthenia continued to be resistant to treatment and her rheumatic disease progressed despite aggressive therapy. We performed a database search of MEDLINE, EMBASE, Scopus, and Web of Science for articles of similar cases post thymectomy from inception to August 2021, using the terms "systemic lupus erythematosus" (or systemic sclerosis, or connective tissue disease) and "myasthenia gravis" and "thymectomy". We identified 41 cases, 28 of SLE post thymectomy, 8 related to systemic sclerosis, 5 with mixed connective tissue disease and highlighted their different presentation and serology. We explore the role of the thymus, tolerance and myasthenia gravis in the development of connective tissue disease. This highlights the complexity of concurrent autoimmune diseases and their autoantibodies.

Thymoma with osseous metaplasia; a case report with a brief literature review

INTRODUCTION AND IMPORTANCE

The thymus is a primary lymphatic organ within the mediastinum that plays an essential role in developing and maintaining cell-mediated immunity. The current study aims to report a case of intra-tumoral osseous metaplasia of the thymus gland, which is an infrequent phenomenon.

CASE PRESENTATION

A 43-year-old male presented with weakness and easy fatigability for 2 months. The patient had an elevated anti-acetylcholinesterase antibody (19.5 nmole/L). Magnetic resonance imaging showed a round, capsulated, enhanced mass in the anterior mediastinum measuring 5.5 × 3.5 cm, suspecting thymoma. The patient underwent plasmapheresis three times in one week, under general anesthesia, in a supine position, sternotomy was performed, and the thymoma was totally resected.

DISCUSSION

Thymomas are known to occur in all age groups with the peak of nearly between 35 and 70 years with the median age of 54 years. The sex distribution of thymoma is approximately equal with slight predilection of women in old age groups. However, among all reported cases of thymomas with osseous metaplasia, the majorities are female. The significance of this ossification is still to be clarified.

CONCLUSION

Although it is rare, secondary changes in thymoma may occur including calcification and ossification.