Three types of striational antibodies in myasthenia gravis

Toward European harmonization of national myasthenia gravis registries: modified Delphi procedure-based expert consensus on collectable data

BACKGROUND

Myasthenia gravis (MG) is a rare autoimmune disorder. Several new treatment concepts have emerged in recent years, but access to these treatments varies due to differing national reimbursement regulations, leading to disparities across Europe. This highlights the need for high-quality data collection by stakeholders to establish MG registries. A European MG registry could help bridge the treatment access gap across different countries, offering critical data to support regulatory decisions, foster international collaborations, and enhance clinical and epidemiological research. Several national MG registries already exist or are in development. To avoid duplication and ensure harmonization in data collection, a modified Delphi procedure was implemented to identify essential data elements for inclusion in national registries.

RESULTS

Following a literature review, consultations with patient associations and pharmaceutical companies, and input from multiple European MG experts, 100 data elements were identified. Of these, 62 reached consensus for inclusion and classification, while only 1 item was agreed for exclusion. 30 items failed to reach the ≥ 80% agreement threshold and were excluded. Among the 62 accepted items, 21 were classified as mandatory data elements, 32 optional, and 9 items pertained to the informed consent form.

CONCLUSIONS

Through a modified Delphi procedure, consensus was successfully achieved. This consensus-based approach represents a crucial step toward harmonizing MG registries across Europe. The resulting dataset will facilitate the sharing of knowledge and enhance European collaborations. Furthermore, the harmonized data may assist in regulatory or reimbursement decisions regarding novel therapies, as well as address treatment access disparities between European countries.

Autoantibodies in myasthenia gravis: cluster analysis and clinical correlations

Objective

This study aimed to explore autoantibody clusters and their correlations with clinical features in 644 myasthenia gravis (MG) patients.

Methods

Medical records of 664 MG patients were reviewed. Five autoantibodies (AChR, MuSK, titin, RyR, and LRP4) were selected for cluster analysis. The various clinical manifestations were compared between clusters. Separate association analyses between individual autoantibodies and clinical manifestations as well as among different MGFA subtypes were also performed without prior clustering.

Results

Two separate autoantibody clusters were identified, with significantly different clinical manifestations. Cluster 1 (485 patients) was characterized by higher proportions of RyR-, titin-, and AChR-, while cluster 2 (179 patients) had higher proportions of RyR+, titin+, and AChR+. Cluster 2 patients were older and had elevated QMG scores and odds of complications, particularly hypertension, diabetes, cardiovascular and cerebrovascular diseases, and eye conditions. Individual antibody analysis revealed that male cases were more likely to be AChR+ and titin+, and older age was associated with AChR+, RyR+, and titin+. Among MGFA subtypes, significant differences were detected in AChR, MuSK, titin, complications, thymoma, and hypertension. As MG severity increased from types I to V, AChR+, RyR+, and titin+ proportions peaked at stage IIa. MuSK+ patients were relatively rare and mostly present in the subtype b group. Type b patients had higher MuSK+ prevalence and increased cardiovascular and cerebrovascular disease incidence rates than type a cases.

Conclusion

Overall, cluster 2 features were less favorable to patients. This study provides valuable insights into the clinical and autoantibody profiles of Chinese MG patients.

A Rare Case of Overlapping Durvalumab-induced Myositis, Takotsubo-like Morphological Changes Caused by Myocarditis, and Myasthenia Gravis

Immune checkpoint inhibitors can cause a range of immune-related adverse events, including myositis, Takotsubo cardiomyopathy, and myasthenia gravis. We herein report a rare case of a 78-year-old man with concurrent durvalumab-induced myositis, Takotsubo-like morphological changes caused by myocarditis, and myasthenia gravis. The patient initially required invasive ventilation and exhibited symptoms of myasthenia gravis after treatment with high-dose steroids. However, he subsequently achieved successful recovery after the administration of intravenous immunoglobulin, plasmapheresis, and high-dose steroids. We advocate vigilant neurological monitoring of patients with immune checkpoint inhibitor-induced myositis, including the assessment of ptosis and other relevant signs, so that prompt treatment can be initiated at the time of emergence or progression of immune checkpoint inhibitor-induced myasthenia gravis.

Cardiac implications in myasthenia gravis

This editorial aimed to consolidate the current evidence in literature on the association between myasthenia gravis (MG) and cardiac involvement, focusing on the impact of thymoma, antistriational antibodies, and late-onset MG. Additionally, the study aimed to explore the influence of genetic differences among populations on the association with cardiac disease. We conducted a review of existing literature in PubMed and Google Scholar to find relevant studies on cardiac involvement in MG. We created search criteria using a combination of free text words, including MG, antistriational antibodies, thymectomy, cardiomyopathy, myocarditis, arrhythmias, autonomic dysfunction. Relevant articles published in English language were analyzed and incorporated. The findings indicate a strong association between thymoma, myasthenic crisis, antistriational antibodies, and late-onset MG with cardiac involvement. The study also revealed that genetic differences among populations influence the risk of cardiac disease and electrocardiography (ECG) abnormalities in MG patients. Autonomic dysfunctions altered cardiac autonomic response and increased susceptibility to arrhythmias and sudden cardiac death in MG patients. The study supports the significance of thymoma, antistriational antibodies, and late-onset MG as key factors associated with cardiac involvement in MG patients. It emphasizes the importance of ECG as the initial test in managing MG patients, particularly in the perioperative period, to identify and genetic testing if needed to address their cardiac risk effectively.

Protein networking: nicotinic acetylcholine receptors and their protein-protein-associations

Nicotinic acetylcholine receptors (nAChR) are complex transmembrane proteins involved in neurotransmission in the nervous system and at the neuromuscular junction. nAChR disorders may lead to severe, potentially fatal pathophysiological states. To date, the receptor has been the focus of basic and applied research to provide novel therapeutic interventions. Since most studies have investigated only the nAChR itself, it is necessary to consider the receptor as part of its protein network to understand or elucidate-specific pathways. On its way through the secretory pathway, the receptor interacts with several chaperones and proteins. This review takes a closer look at these molecular interactions and focuses especially on endoplasmic reticulum biogenesis, secretory pathway sorting, Golgi maturation, plasma membrane presentation, retrograde internalization, and recycling. Additional knowledge regarding the nAChR protein network may lead to a more detailed comprehension of the fundamental pathomechanisms of diseases or may lead to the discovery of novel therapeutic drug targets.

Perioperative cardiac risks in myasthenia gravis

Myasthenia gravis (MG) is an autoimmune disorder that affects the neuromuscular junction. The primary pathology in MG involves the presence of autoantibodies to acetylcholine receptors (AChRs), which results in qualitative and quantitative reductions in the availability of functional AChRs. Cardiac muscles are also affected, resulting in various perioperative cardiac complications. Antistriational antibodies are commonly reported in MG cases with cardiac involvement. In the presence of thymoma, the prevalence of cardiac manifestations in patients with MG increases to approximately 10%-15%. Cardiac involvement in MG may range from asymptomatic electrocardiogram changes to ventricular tachycardia, myocarditis, conduction disorders, heart failure, and sudden death. Increased incidence of atrial fibrillation, ventricular and supraventricular extra systoles, and prolonged QTc have also been reported in patients with MG. Clinicians should consider the evaluation of autonomic dysfunction and risk of cardiovascular disease in patients with MG.

[A case of anti-acetylcholine receptor antibody-positive ocular myasthenia gravis with anti-titin antibody and anti-Kv1.4 antibody positive inflammatory myopathy]

An 84-year-old man was diagnosed with anti-acetylcholine receptor (AChR) antibody-positive ocular myasthenia gravis (OMG) at the age of 77 and received treatment. The patient was referred to our department with swelling and pain in his right upper arm, which had spread to other limbs. His serum anti-AChR antibody and creatine kinase levels were elevated, and MRI of the limbs displayed signal changes suggesting inflammation in the several muscles. Despite showing no sign of thymoma, he was positive for serum anti-titin and anti-Kv1.4 antibodies. We performed a muscle biopsy, which led to a diagnosis of inflammatory myopathy (IM). IM associated with OMG is relatively mild. Age-related immune dysregulation may cause both OMG and IM. Evaluation of disease activity with serum anti-AChR antibody levels, and assessment of prognosis with examining anti-striational antibodies are necessary for appropriate management of IM associated with MG.

Case Report: Telitacicept in severe myasthenia gravis: a case study with multiple autoantibodies

Multi-antibody-positive myasthenia gravis (MG) presentations are relatively rare, often found in older patients, and generally predict a poor prognosis. We report a case of a female patient with generalized MG, testing positive for Titin antibodies (Titin-Ab), ryanodine receptor antibodies (RyR-Ab), and acetylcholine receptor antibodies (AChR-Ab), and resistant to acetylcholinesterase inhibitors. Following unsuccessful traditional therapies, she received Telitacicept, leading to significant improvements. This case underscores Telitacicept's potential efficacy for similar patients and offers insights into the clinical characteristics of multi-antibody MG.

Anti-Kv1.4 Antibody-positive Nivolumab-induced Myasthenia Gravis and Myositis Presenting with Bilateral Ptosis and Demonstrating Different Pathophysiologies

Nivolumab blocks inhibitors of T-cell activation and restores antitumor immunity but promotes T-cell activity in host tissues by blocking inhibition of the T-cell function, resulting in immune-related adverse effects. We herein report an 80-year-old man presenting with nivolumab-related myasthenia gravis with anti-muscular voltage-gated potassium channel-complex (Kv1.4) antibodies. On day 29 after nivolumab administration, he simultaneously developed rapidly progressing right ptosis and left facial paralysis. Nivolumab administration was discontinued. He subsequently presented with bulbar paralysis, dyspnea, and muscle weakness and received intravenous immunoglobulin, methylprednisolone, and plasma exchange. The severity of nivolumab-related myasthenia gravis with anti-Kv1.4 antibodies presented with diverse clinical findings.

Thymoma-Associated Myasthenia Gravis With Myocarditis

Myasthenia gravis (MG) complicated by myocarditis is a rare autoimmune manifestation. We present a patient who initially presented with a suspected ST-segment elevation myocardial infarction (STEMI) with angiographically normal coronary arteries. A chest CT scan revealed a large homogenous soft-tissue density anterior mediastinal mass suspicious of thymoma. Neurological deterioration in the hospital suggested a diagnosis of MG with subsequent electromyography and nerve conduction studies (EMG/NCS) and repetitive nerve stimulation (RNS) confirmation. A cardiac magnetic resonance imaging study (CMR) demonstrated diffuse myocardial edema and severe left ventricular (LV) dysfunction and sub-epicardial late gadolinium enhancement (LGE) involving all basal and mid-LV segments in addition to apical inferior and lateral segments. A diagnosis of thymoma-associated MG with myocarditis was made and the patient was successfully treated with immunosuppression. This case highlights the association of myocarditis with MG as a potential complication that should be considered in patients with cardiac symptoms, ECG changes, or biomarker elevation.

Peripheral nervous system adverse events associated with immune checkpoint inhibitors

BACKGROUND

Immune checkpoint inhibitors (ICIs) represent an effective cancer immunotherapy yet are associated with immune-related adverse events (irAEs). The aim of this study was to characterize irAEs involving the peripheral nervous system (PNS-irAEs) in a real-world cohort of ICI-treated patients.

METHODS

Cancer patients treated with ICIs between January 2014 and March 2022 were included. Patients with PNS-irAEs were identified and divided into two groups: (1) cranial/peripheral neuropathies and (2) myasthenia gravis (MG) and/or myositis. Clinical characteristics and outcomes, measured with the modified Rankin Scale (mRS), were compared among the two groups.

RESULTS

Among 920 ICI-treated patients, 20 patients (2.17%) developed a PNS-irAEs. The median latency from ICI exposure was 8.8 weeks and the median time from onset to clinical nadir was 3.5 weeks. Eleven patients developed a neuropathy: polyneuropathy (n = 4), cranial neuropathy (n = 3), small-fiber neuropathy (n = 3), brachial plexopathy (n = 1). Nine patients presented MG and/or myositis: concomitant MG and myositis (n = 6), isolated myositis (n = 2), exacerbation of MG (n = 1). Immunosuppressive treatment and/or ICI withdrawal determined a significant clinical improvement, expressed by a mRS reduction, in the neuropathy group (p = 0.004), but not in the MG/myositis group (p = 0.11). Overall, death due to irAEs occurred in four patients (20%), all with MG/myositis. Compared to patients with neuropathies, those with MG/myositis had a shorter latency onset (p = 0.036), developed more frequently concomitant non-neurologic irAEs (p = 0.028) and showed a higher mortality rate (p = 0.026).

CONCLUSIONS

In our large cohort of ICI-treated patients, 2.17% developed PNS-irAEs. Compared to ir-neuropathies, ir-MG/myositis tend to occur earlier from ICI exposure and present a worse response to treatment and a higher mortality.

Myocardial Injury in Hospitalized Patients with Myasthenia Gravis

Objective: To investigate the clinical characteristics and outcome of myocardial injury in patients with myasthenia gravis (MG). Methods: We retrospectively searched medical records to screen hospitalized patients with MG at our hospital. The troponin T (TnT) levels were deemed necessary to be performed based on the patient’s clinical symptoms and were used as biomarkers of myocardial injury. The patients’ demographic and clinical information were collected. Death was the primary outcome. Results: A total of 336 patients with MG measured TnT levels and were included in the final analysis. The male MG patients with elevated TnT levels had a higher prevalence of infection (56.8% vs. 30.0%, p = 0.001) and myasthenic crisis (37.5% vs. 13.3%, p = 0.001) than those with normal TnT levels. Meanwhile, the female MG patients with elevated TnT levels were older (56.0 (16.6) vs. 49.2 (17.2)) years old, p = 0.007] and had a higher prevalence of infection (65.4% vs. 32.1%, p < 0.001), myasthenic crisis (33.6% vs. 17.9%, p = 0.015), and thymoma (38.5% vs. 16.7%, p = 0.001) than those with normal TnT levels. Older age (coef. = 0.004; p = 0.034), infection (coef. = 0.240; p = 0.001), myasthenic crisis (coef. = 0.312; p < 0.001), thymoma (coef. = 0.228; p = 0.001), and ICI therapy (coef. = 1.220; p < 0.001) were independent risk predictors for increasing log TnT levels. Thirty-seven patients died during hospitalization. High log TnT levels (OR = 8.818; p < 0.001), female sex (OR = 0.346; p = 0.023), thymoma (OR = 5.092; p = 0.002), and infection (OR = 14.597; p < 0.001) were independent risk predictors of death. Conclusions: Our study revealed that the surveillance of myocardial injury biomarkers in MG patients might be beneficial.

Nivolumab-induced Myositis and Myocarditis with Positive Anti-titin Antibody and Anti-voltage-gated Potassium Channel Kv1.4 Antibody

Immune checkpoint inhibitors (ICIs) are complicated by immune-related adverse events (irAEs), such as myositis, myocarditis, and myasthenia gravis (MG). Anti-titin antibody and anti-voltage-gated potassium channel Kv1.4 antibody are anti-striated antibodies that are frequently detected in MG patients with myositis and/or myocarditis. However, the clinical relationship between positive anti-striated antibodies and irAEs of ICIs remains unknown. We herein report a case of nivolumab-induced myositis and myocarditis with positive anti-titin antibody and anti-voltage-gated potassium channel Kv1.4 antibody in a patient with non-small-cell lung cancer. We also review reported cases of positive anti-striated antibodies related to irAEs of ICIs.

Acquired myasthenia gravis with concurrent polymyositis and myocarditis secondary to a thymoma in a dog

Background:

Canine thymomas are associated with multiple paraneoplastic syndromes, among which myasthenia gravis (MG) is the most common. Acquired MG is an autoimmune disease characterized by the presence of antibodies against acetylcholine receptors (ACHRs). ACHRs antibodies are the most commonly formed, but the production of antistriational antibodies binding to skeletal and cardiac muscle proteins has also been recorded both in humans and dogs. An association between the occurrence of antistriational antibodies and a severe form of myocarditis, giant cell myocarditis, has been described in humans.

Case Description:

A 4-year-old mixed-breed dog was referred because of 1 month history of exercise-induced weakness, hypersalivation, and regurgitation. The neurologic examination was indicative of a neuromuscular junction disease, and MG was suspected. A computed tomographic scan examination showed the presence of a megaoesophagus and a thymic mass. Serum antibodies against ACHRs confirmed the diagnosis of MG. Treatment with pyridostigmine was started, and the thymic mass was surgically excised, and a diagnosis of thymoma was confirmed by histology. 24 hours after surgery, the dog developed a third-degree atrioventricular block. Severe arrhythmia and increased troponin serum levels suggested myocarditis which rapidly led to cardiopulmonary arrest. Histopathologic examination of the heart, esophagus and diaphragm revealed a lymphocytic and macrophagic infiltration, consistent with myocarditis and polymyositis. Scattered rare giant multinucleated cells were also detected in the myocardium.

Conclusion:

To the author’s knowledge, this is the first report of thymoma-associated MG with concurrent polymyositis and giant cell-like myocarditis in a dog.

[Immune checkpoint inhibitor-induced anti-striational antibodies in myasthenia gravis and myositis: a case report]

A 78-year-old man was treated with ipilimumab and nivolumab for advanced renal cell carcinoma with liver and lymph node metastasis. He developed diplopia, ptosis, dysphagia, and weakness of the limbs and neck, 1 month after treatment. Serum creatine kinase (CK) levels were elevated, and neck MRI revealed inflammation of the deep trunk muscles. Although anti-acetylcholine receptor antibody was negative, the edrophonium test was positive. Anti-striational antibodies such as the anti-titin and the anti-muscular voltage-gated potassium channel (Kv 1.4) antibodies (which serve as biomarkers of immune checkpoint inhibitors associated with myasthenia gravis and myositis) were positive (anti-titin antibody titer 11.51, normal <1 index; anti-Kv 1.4 antibody titer 15.13, normal <1 index). Intravenous methylprednisolone pulse therapy (1,000 mg/day for 3 days), plasmapheresis, and oral prednisolone (PSL) (20 mg/day) administration improved the patient's neurological function and normalized the serum CK levels. The PSL dosage was tapered without any worsening of clinical signs. The antibody titers decreased but remained positive (anti-titin antibody 5.00, anti-Kv 1.4 antibody 3.83) one year after the initial evaluation. Therefore, low-dose PSL (5 mg/day) administration was continued, and the patient was in remission.

[Anti-striational antibodies detected in a patient with late-onset myasthenia gravis suffering from severe bradycardia: a case report]

We report herein the case of a 79-year-old woman who experienced difficulties in swallowing, dysarthria, dropped head, and muscle weakness associated with diurnal and day-to-day variation. We made a diagnosis of generalized myasthenia gravis (MG) with anti-acetylcholine receptor antibodies. Contrast-enhanced computed tomography showed no sign of thymoma. As the MG worsened, the patient presented with severe bradycardia. Chest compressions were performed on days 6 and 7 after admission and she underwent implantation of a temporary pacemaker. The arrhythmia resolved after strong immunosuppressive treatment, and anti-striational antibodies, including anti-muscular voltage-gated potassium channel-complex (Kv1.4) antibody and anti-titin antibody, were subsequently detected. This case implies the possible involvement of anti-striational antibodies in bradycardia.

Giant cell myositis associated with concurrent myasthenia gravis: a case-based review of the literature

The term “giant cell myositis” has been used to refer to muscle diseases characterized histologically by multinucleated giant cells. Myasthenia gravis is an autoimmune neuromuscular junction disorder. The rare concurrence of giant cell myositis with myasthenia gravis has been reported; however, the clinical and histological features have varied widely. Here, we present such a case and a review of the literature. An 82-year-old woman admitted for subacute, progressive, proximal muscle weakness developed acute-onset dysphagia, dysphonia, and respiratory distress 5 days after admission. Laboratory findings were positive for acetylcholine receptor binding antibodies and striational muscle antibodies against titin. Muscle biopsy demonstrated widespread muscle fiber necrosis with multinucleated giant cells, consistent with giant cell myositis. She died despite treatment with pulse methylprednisolone and plasma exchange. A literature review of the PubMed and Scopus databases from 1944 to 2020 identified 15 additional cases of these co-existing diagnoses. We found that giant cell myositis with myasthenia gravis primarily affects female patients, is typically diagnosed in the 6–7th decades, and is characterized by the presence of thymoma. Muscle histology predominantly shows giant cell infiltrate without granulomas. The onset of myasthenia gravis symptoms may precede, follow, or coincide with symptoms of myositis. Treatment with thymectomy, anticholinesterase inhibitors, or immunosuppressive therapy may lead to favorable clinical outcomes.

Myasthenia gravis: MuSK MG, late-onset MG and ocular MG

Myasthenia gravis (MG) is an autoimmune disease of the neuromuscular junction which affects all striated muscles, resulting in fluctuating weakness. Approaching MG as a disease with subgroups having different clinical, serological and genetic features is crucial in predicting the progression and planning treatment. Three relatively less frequently seen subtypes of MG are the subject of this review: MG with anti-MuSK antibodies (MuSK MG), non-thymomatous late-onset MG (LOMG), and ocular MG (OMG). In addition to reviewing the literature, mainly from a clinical point of view, our experience in each of the subgroups, based on close to 600 patients seen over a 10 year period, is related. MuSK MG is a severe disease with predominant bulbar involvement. It is more common in women and in early-onset patients. With the use of high dose corticosteroids, azathioprine and more recently rituximab, outcome is favorable, though the patients usually require higher maintenance doses of immunosuppressives. LOMG with onset ≥ 50 years of age is more common in men and ocular onset is common. Frequency of anti-AChR and anti-titin antibodies are high. Although it can be severe in some patients, response to treatment is usually very good. OMG is reported to be more frequent in men in whom the disease has a later onset. Anti-AChR antibodies are present in about half of the patients. Generalization is less likely when symptoms remain confined to ocular muscles for 2 years. Low dose corticosteroids are usually sufficient. Thyroid disease is the most common autoimmune disease accompanying all three subgroups.

Anti-MuSK Positive Myasthenia Gravis with Anti-Lrp4 and Anti-titin Antibodies

In addition to muscle nicotinic acetylcholine receptor (AChR) and muscle-specific kinase (MuSK), low-density lipoprotein receptor (Lrp4) has recently been discovered to be a novel target antigen among patients with seronegative myasthenia gravis (MG). We herein report the findings of a 62-year-old patient who showed positivity for anti-MuSK, anti-Lrp4, and anti-titin antibodies. The patient developed MG crisis following a 10-year history of intermittent double vision with ptosis, and a 7-year history of dropped head. Our detailed clinical, laboratory, and therapeutic descriptions highlight its unique characteristics of anti-MuSK-antibody positive MG accompanied by anti-Lrp4 and anti-titin antibodies.

Neuroimmunogastroenterology: At the Interface of Neuroimmunology and Gastroenterology

The central nervous system (CNS) is an important regulator of the gastrointestinal tract, and CNS dysfunction can result in significant and disabling gastrointestinal symptom manifestation. For patients with neuroimmunologic and neuroinflammatory conditions, the recognition of gastrointestinal symptoms is under-appreciated, yet the gastrointestinal manifestations have a dramatic impact on quality of life. The current treatment strategies, often employed independently by the neurologist and gastroenterologist, raise the question of whether such patients are being treated optimally when siloed in one specialty. Neuroimmunogastroenterology lies at the borderlands of medical specialties, and there are few resources to guide neurologists in this area. Here, we provide an overview highlighting the potential mechanisms of crosstalk between immune-mediated neurological disorders and gastrointestinal dysfunction.

[A case of sporadic late-onset nemaline myopathy associated with myasthenia gravis positive for anti-titin antibody and anti-Kv1.4 antibody]

A 66-year-old woman who had myasthenia gravis (MG) admitted for type II respiratory failure and right heart failure. Although she had neither ptosis, eye movement disorder, nor diplopia, she had orbital muscles weakness, reduction of gag reflex, dysarthria, dysphagia, and mild proximal muscle weakness. Blood tests showed anti-striated muscle antibodies (anti-titin antibody and anti-Kv1.4 antibody). A muscle biopsy of the left biceps showed a marked variation in fiber size, mild mononuclear cell infiltration was seen surrounding blood vessels in perimysium and nemaline bodies in some fibers. Immunohistochemical stains showed many muscle fibers express HLA-ABC. The patient was diagnosed as sporadic late-onset nemaline myopathy (SLONM) with MG, and treated by tacrolimus. After treatment, her respiratory function gradually improved and she discharged. In the case of atypical MG, measurement of anti-striated muscle antibody or muscle biopsy should be considered.

[A case of myasthenia gravis developed during pembrolizumab administration, suggesting an excitation-contraction connection disorder]

The patient was a 50-year-old woman. Pembrolizumab was started for bladder cancer recurrence. From the day after the second administration, ptosis, diplopia, restriction of eye movement, muscle weakness, fatigue resistance, increase in serum creatine kinase (CK) level, and muscle pain were observed. Tests for anti-acetylcholine receptor (AChR) antibody and anti-muscle specific kinase (MuSK) antibody were negative. Electrophysiological examination of the neuromuscular junction showed negative results, and electromyography revealed no myogenic changes. We considered that the immune checkpoint inhibitor caused neuromuscular damage. The patient's symptoms were gradually improved by immunotherapy, such as steroid and plasma exchange. In this case, tests for the anti-titin antibody, an anti-striational antibody, were positive. We considered that myasthenia gravis-like symptoms and serum CK level elevation might have been caused by impairment of excitation-contraction coupling, and not the neuromuscular junction.

[A case of myasthenia gravis and myositis induced by pembrolizumab]

A 77-year-old woman with lung adenocarcinoma noticed bilateral ptosis 7 weeks after a first pembrolizumab infusion. Her symptoms rapidly progressed to generalized manifestations including limb and neck weakness, dyspnea, and dysphasia within the following two weeks. We diagnosed him with pembrolizumab-related myasthenia gravis and myositis based on clinical symptoms, elevation of muscle enzymes and anti-acetylcholine receptor antibodies, repetitive nerve stimulation and muscle biopsy. We commenced combination immunotherapy, including intravenous and oral steroid therapy, immune absorption therapy and plasma exchange therapy with noninvasive positive-pressure ventilation and tracheotomy positive pressure ventilation. She had gradual symptoms improvement and discharged after 209 days in a hospital. In this case, anti-titin antibodies, one of anti-striational antibodies, was positive and correlated with severity of myasthenia gravis. With the development of immune checkpoint inhibitors for various malignancies, clinicians should closely monitor patients for important immune-related adverse events and coordinate on early treatment.

Presence of Multiple Autoimmune Antibodies Involved in Concurrent Myositis and Myocarditis and Myasthenia Gravis Without Thymoma: A Case Report

Inflammatory myositis (IM) and myasthenia gravis (MG) are both immune disorders involving muscle. The concurrent presence of both conditions in the same patient is extremely rare and the diagnosis is important and challenging. Here, we report a case of concurrent myositis and myocarditis and MG without thymoma in a 69-year-old man with progressive proximal muscle weakness and dysphagia. As an atypical finding, the laboratory immunity assay showed the presence of multiple antibodies (acetylcholine receptor-Ab, titin-Ab, M7-Ab, smooth muscle alpha (SMA)-Ab, and citrate acid extract (CAE)-Ab). We predicted that thymoma-associated antibodies (titin-Ab, SMA-Ab, and CAE-Ab) and anti-M7 antibodies play an important role in the concurrent presence of MG and myositis and myocarditis. In this overlap case, immunotherapy was determined to be effective.

Granulomatous Myositis Associated with Myasthenia Gravis: A Rare Case

Myasthenia gravis (MG) is an immune-mediated disease of the neuromuscular junction mediated by anti-acetylcholine receptor (AChR) antibodies (Ab). Granulomatous Myositis (GrM) is a histological diagnosis characterized by the presence of epithelioid granuloma in striated muscles. Few cases describing the presence of concomitant thymoma and non-thymoma-related MG with GrM have been reported. This present case is an addition to the literature describing the presence of concomitant thymoma and non-thymoma-related MG with GrM. The patient described is a 77-year-old male who started developing weakness and atrophy involving the musculature of the bilateral lower and upper extremities. Initial laboratory workup showed an elevated level of serum creatine phosphokinase (CPK) of 1,231 U/ L (reference range: 22 to 198 U/L). The right quadriceps muscle biopsy performed showed inflammatory infiltrates containing eosinophils, plasma cells, and lymphocytes forming multinucleate giant cells consistent with a diagnosis of GrM. Detailed laboratory and imaging work conducted to rule out an underlying cause of GrM showed elevated titers of AChR Ab (79.50 nmol/L, reference range: <0.02 nmol/L) and striational Ab (titer: 1:320, reference range < 1:120). A positive repetitive nerve stimulation test for the left ulnar nerve (decrement in the amplitude of muscle action potential by 13%) further confirmed the diagnosis of MG concomitant with GrM. Computed tomography of the chest was negative for the presence of a thymoma. The patient was started on treatment with oral prednisone and mycophenolate mofetil, which resulted in an improvement of symptoms and the downward trending of serum CPK level.

Myasthenia Gravis: Pathogenic Effects of Autoantibodies on Neuromuscular Architecture

Myasthenia gravis (MG) is an autoimmune disease of the neuromuscular junction (NMJ). Autoantibodies target key molecules at the NMJ, such as the nicotinic acetylcholine receptor (AChR), muscle-specific kinase (MuSK), and low-density lipoprotein receptor-related protein 4 (Lrp4), that lead by a range of different pathogenic mechanisms to altered tissue architecture and reduced densities or functionality of AChRs, reduced neuromuscular transmission, and therefore a severe fatigable skeletal muscle weakness. In this review, we give an overview of the history and clinical aspects of MG, with a focus on the structure and function of myasthenic autoantigens at the NMJ and how they are affected by the autoantibodies' pathogenic mechanisms. Furthermore, we give a short overview of the cells that are implicated in the production of the autoantibodies and briefly discuss diagnostic challenges and treatment strategies.

Pembrolizumab-induced Ocular Myasthenia Gravis with Anti-titin Antibody and Necrotizing Myopathy

A 73-year-old man developed diplopia after the administration of pembrolizumab for lung adenocarcinoma. He had ptosis and external ophthalmoplegia without general muscle weakness. Serum CK levels were elevated. Although autoantibodies to acetylcholine receptor and muscle-specific kinase, the edrophonium test, and the repetitive nerve stimulation test were all negative, anti-titin autoantibody was positive, leading to the diagnosis of myasthenia gravis (MG). Muscle pathology showed necrotizing myopathy with tubular aggregates. Unlike previously reported cases of pembrolizumab-associated MG, the present case showed ocular MG. This is the first case of pembrolizumab-associated MG with anti-titin antibody, as well as the first case with tubular aggregates.

Bilateral pseudo-internuclear ophthalmoplegia in a patient with myasthenia gravis

Purpose

To report a case of myasthenia gravis presenting with a false localizing sign, a bilateral pseudo internuclear ophthalmoplegia.

Observations

A 61 year-old male presented with a five-week history of painless binocular oblique diplopia that was associated with fatigue, vocal hoarseness and bilateral ptosis, the latter two of which worsened through the course of the day. Exam was remarkable for an apparent bilateral internuclear ophthalmoplegia (INO). MRI of the brain with and without contrast and MRA of the head and neck were within normal limits. Lab work was positive for anti-AChR binding, blocking, and modulating antibodies, as well as anti-striated muscle and anti-titin antibodies. The patient was initiated on therapy for myasthenia gravis.

Conclusion and importance

Although myasthenia gravis often presents with ptosis or diplopia, rarely patients may develop pseudo-INO secondary to extraocular muscle weakness. True INO occurs with damage to the medial longitudinal fasciculus, a myelinated tract of fibers that controls yoked horizontal eye movements. Clinicians should be suspicious of the false localizing sign of a pseudo-INO associated with myasthenia gravis when more common causes of INO have been excluded.

A diagnosis of late-onset Myasthenia gravis unmasked by topical antibiotics

Myasthenia Gravis (MG) is a disorder of the neuromuscular junction (NMJ) that manifests as fluctuating fatiguable weakness of the muscles. There are many factors that can exacerbate myasthenia symptoms including a variety medications and drugs, systemic illness, and pregnancy. A number of medications have been implicated in exacerbating MG symptoms, including aminoglycosides. We present a case of an elderly female with newly diagnosed MG following the use of tobramycin eye drops for 3 days. There have been limited reports in the literature of topical medications that exacerbate MG symptoms. Clinicians prescribing tobramycin eye drops (or other associated medications) should have a high index of suspicion of MG as early discontinuation and therapy will limit long-term morbidity and mortality in these patients.

A case of late-onset, thymoma-associated myasthenia gravis with ryanodine receptor and titin antibodies and concomitant granulomatous myositis

BACKGROUND

Myasthenia gravis is an autoimmune neuromuscular disorder, which has only rarely been reported to co-manifest with myositis. The diagnosis of concomitant myositis in patients with myasthenia gravis is clinically challenging, and requires targeted investigations for the differential diagnosis, including EMG, autoantibody assays, muscle biopsy and, importantly, imaging of the mediastinum for thymoma screening.

CASE PRESENTATION

This report presents a case-vignette of a 72-year-old woman with progressive proximal muscle weakness and myalgias, diagnosed with thymoma-associated myasthenia and bioptically verified granulomatous myositis, with positive autoantibody status for ryanodine receptor and titin antibodies.

CONCLUSIONS

The diagnosis of concurrent myositis and myasthenia gravis, especially in the presence of ryanodine receptor and titin antibodies, should lead neurologists to adopt different treatment strategies compared to those applied in myasthenia or myositis alone. Moreover, further evidence is warranted that titin and, particularly, ryanodine receptor antibodies may co-occur or be pathophysiologically involved in myasthenia-myositis cases.

An Overview of Cardiac Management in Neuromuscular Disease

Muscular dystrophy and myasthenia gravis are two neuromuscular disorders that can involve significant cardiovascular complications. The frequency and severity of cardiac pathology varies widely among the muscular dystrophies. In some, it is nearly inevitable and requires regular evaluation. In others, assessment of cardiac function can be more symptom-driven. On-ly a minority of myasthenic patients manifest disease-related cardiovascular complications; however, their presentation can be rapidly progressive and life-threatening..

Simultaneous Combined Myositis, Inflammatory Polyneuropathy, and Overlap Myasthenic Syndrome

Immune-mediated neuromuscular disorders include pathologies of the peripheral nervous system, neuromuscular junction, and muscles. If overlap syndromes (or the association of almost two autoimmune disorders) are recognized, the simultaneous occurrence of several autoimmune neuromuscular disorders is rare. We describe two patients presenting the simultaneous occurrence of inflammatory neuropathy, myositis, and myasthenia gravis (with positive acetylcholine receptor antibodies). For each patient, we carried out a pathological analysis (nerve and muscle) and an electrophysiological study (and follow-up). To our knowledge, this is the first description of such a triple immune-mediated neuromuscular syndrome. We compared our observations with a few other cases of simultaneous diagnosis of two inflammatory neuromuscular disorders.

Complicating autoimmune diseases in myasthenia gravis: a review

Myasthenia gravis (MG) is a rare autoimmune disease of skeletal muscle endplates. MG subgroup is relevant for comorbidity, but usually not accounted for. MG patients have an increased risk for complicating autoimmune diseases, most commonly autoimmune thyroid disease, systemic lupus erythematosus and rheumatoid arthritis. In this review, we present concomitant autoimmune disorders associated with the different MG subgroups, and show how this influences treatment and prognosis. Concomitant MG should always be considered in patients with an autoimmune disorder and developing new neuromuscular weakness, fatigue or respiratory failure. When a second autoimmune disorder is suspected, MG should be included as a differential diagnosis.

[A case of myasthenia gravis presenting solely with bulbar palsy unassociated with easy fatigability]

A 69-year-old Japanese female was admitted because of progressive nasal voice and dysphagia. Neurological examination revealed paresis of the soft palate with marked dysphagia and rhinolalia. Otherwise there was no weakness or easy fatigability in extraocular muscles and extremities. On laboratory test, anti-acetylcholine receptor antibody (anti-AChR Ab) was positive, while anti-muscle-specific tyrosine kinase antibody (anti-MuSK Ab) was negative. Edrophonium test was positive, resulting in clear improvement in phonation and swallowing. Harvey-Masland test of ocular and extremity muscles did not show any waning. With the diagnosis of bulbar myasthenia gravis, the patient was treated with methylprednisolone and pyridostigmine, resulting in clear improvement of the symptoms. The present case shows that it is important to consider MG even in cases presenting solely with progressive bulbar palsy without easy fatigability. So far, cases of bulbar myasthenia gravis with positive anti-MuSK Ab have often been reported. As shown in the present case, bulbar myasthenia gravis can also be associated with positive anti-ACh-R Ab but negative anti-MuSK Ab.

Muscle autoantibodies in myasthenia gravis: beyond diagnosis?

Myasthenia gravis is an autoimmune disorder of the neuromuscular junction. A number of molecules, including ion channels and other proteins at the neuromuscular junction, may be targeted by autoantibodies leading to abnormal neuromuscular transmission. In approximately 85% of patients, autoantibodies, directed against the postsynaptic nicotinic acetylcholine receptor can be detected in the serum and confirm the diagnosis, but in general, do not precisely predict the degree of weakness or response to therapy. Antibodies to the muscle-specific tyrosine kinase are detected in approximately 50% of generalized myasthenia gravis patients who are seronegative for anti-acetylcholine receptor antibodies, and levels of anti-muscle-specific tyrosine kinase antibodies do appear to correlate with disease severity and treatment response. Antibodies to other muscle antigens may be found in the subsets of myasthenia gravis patients, potentially providing clinically useful diagnostic information, but their utility as relevant biomarkers (measures of disease state or response to treatment) is currently unclear.

Anti-voltage-gated potassium channel Kv1.4 antibodies in myasthenia gravis

Myasthenia gravis (MG) is an autoimmune disease characterized by skeletal muscle weakness mainly caused by acetylcholine receptor antibodies. MG can be divided into generalized and ocular, and into early-onset (<50 years of age) and late-onset (≥50 years of age). Anti-Kv1.4 antibodies targeting α-subunits (Kv1.4) of the voltage-gated potassium K(+) channel occurs frequently among patients with severe MG, accounting for 18% of a Japanese MG population. The aim of this study was to characterize the clinical features and serological associations of anti-Kv1.4 antibodies in a Caucasian MG population with mild and localized MG. Serum samples from 129 Caucasian MG patients with mainly ocular symptoms were tested for the presence of anti-Kv1.4 antibodies and compared to clinical and serological parameters. There were 22 (17%) anti-Kv1.4 antibody-positive patients, most of them women with late-onset MG, and all of them with mild MG. This contrasts to the Japanese anti-Kv1.4 antibody-positive patients who suffered from severe MG with bulbar symptoms, myasthenic crisis, thymoma, myocarditis and prolonged QT time on electrocardiography, despite equal anti-Kv1.4 antibody occurrence in both populations. No other clinical or serological parameters influenced anti-Kv1.4 antibody occurrence.