Seronegative Myasthenia Gravis Research Articles

B-cell immune dysregulation with low soluble CD22 levels in refractory seronegative myasthenia gravis.

Myasthenia gravis (MG), primarily caused by acetylcholine receptor (AChR) autoantibodies, is a chronic autoimmune disorder causing severe muscle weakness and fatigability. In particular, seronegative MG constitutes 10%-15% of MG cases and presents diagnostic challenges especially in early-onset female patients who often show severe disease and resistance to immunosuppressive therapy. Furthermore, the immunopathology of seronegative MG remains unclear. Thus, in this study, we aimed to elucidate the pathogenic mechanism of seronegative MG using scRNA-seq analysis and plasma proteome analysis; in particular, we investigated the relationship between immune dysregulation status and disease severity in refractory seronegative MG. Employing single-cell RNA-sequencing and plasma proteome analyses, we analyzed peripheral blood samples from 30 women divided into three groups: 10 healthy controls, 10 early-onset AChR-positive MG, and 10 refractory early-onset seronegative MG patients, both before and after intravenous immunoglobulin treatment. The disease severity was evaluated using the MG-Activities of Daily Living (ADL), MG composite (MGC), and revised 15-item MG-Quality of Life (QOL) scales. We observed numerical abnormalities in multiple immune cells, particularly B cells, in patients with refractory seronegative MG, correlating with disease activity. Notably, severe MG cases had fewer regulatory T cells without functional abnormalities. Memory B cells were found to be enriched in peripheral blood cells compared with naïve B cells. Moreover, plasma proteome analysis indicated significantly lower plasma protein levels of soluble CD22, expressed in the lineage of B-cell maturation (including mature B cells and memory B cells), in refractory seronegative MG patients than in healthy donors or patients with AChR-positive MG. Soluble CD22 levels were correlated with disease severity, B-cell frequency, and RNA expression levels of CD22. In summary, this study elucidates the immunopathology of refractory seronegative MG, highlighting immune disorders centered on B cells and diminished soluble CD22 levels. These insights pave the way for novel MG treatment strategies focused on B-cell biology.

Advancements and prospects of novel biologicals for myasthenia gravis: toward personalized treatment based on autoantibody specificities.

Myasthenia gravis (MG) is an antibody-mediated autoimmune disease with a prevalence of 150-250 cases per million individuals. Autoantibodies include long-lived antibodies against the acetylcholine receptor (AChR), mainly of the IgG1 subclass, and IgG4, produced almost exclusively by short-lived plasmablasts, which are prevalent in muscle-specific tyrosine kinase (MuSK) myasthenia gravis. Numerous investigations have demonstrated that MG patients receiving conventional medication today still do not possess satisfactory symptom control, indicating a substantial disease burden. Subsequently, based on the type of the autoantibody and the pathogenesis, we synthesized the published material to date and reached a conclusion regarding the literature related to personalized targeted therapy for MG. Novel agents for AChR MG have shown their efficacy in clinical research, such as complement inhibitors, FcRn receptor antagonists, and B-cell activating factor (BAFF) inhibitors. Rituximab, a representative drug of anti-CD20 therapy, has demonstrated benefits in treatment of MuSK MG patients. Due to the existence of low-affinity antibodies or unidentified antibodies that are inaccessible by existing methods, the treatment for seronegative MG remains complicated; thus, special testing and therapy considerations are necessary. It may be advantageous to initiate the application of novel biologicals at an early stage of the disease. Currently, therapies can also be combined and individualized according to different types of antibodies. With such a wide range of drugs, how to tailor treatment strategies to patients with various conditions and find the most suitable solution for each MG profile are our necessary and urgent aims.

Clinical Features and Pathogenesis of Double Seronegative Myasthenia Gravis

Subjects with double seronegative myasthenia gravis (DNMG) are defined as those who are seronegative to both antibodies against acetylcholine receptor (AChR) and muscle-specific kinase (MuSK) by radioimmunoprecipitation assay (RIA). They are basically heterogeneous. But cell based assay (CBA) with clustered AChR has revealed a considerable part of DNMG are AChR antibody associated. Furthermore, information of clinical features and thymus pathology has raised a possibility that this could extend to those with undetectable antibodies by established assays whose symptoms are mild. Primary sites of antibody production are probably in the thymus in these cases. LOMG pathology is also suspected for a small part of DNMG by age onset, atrophic or age-related thymus and presence of titin antibody. In these cases, tolerance induction may be insufficient, and positive selection of autoimmune T cells such as AChR-specific T cells are promoted rather than negative selection. In addition, CBA detected MuSK antibody associated in a few cases with DNMG. Finally, some DNMG subjects have distinct clinical features with severe symptoms from those with AChR- MG and MuSK-MG in DNMG. They probably have different pathogenesis.

First case recognized as autoimmune polyglandular syndrome type 2 with double seronegative myasthenia gravis - A case report-from Pakistan

First case recognized as autoimmune polyglandular syndrome type 2 with double seronegative myasthenia gravis - A case report-from Pakistan

Rituximab treatment in myasthenia gravis.

Myasthenia gravis (MG) is a chronic autoimmune disease mediated by antibodies against post-synaptic proteins of the neuromuscular junction. Up to 10%-30% of patients are refractory to conventional treatments. For these patients, rituximab has been used off-label in the recent decades. Rituximab is a monoclonal antibody against the CD20 protein that leads to B cell depletion and to the synthesis of new antibody-secreting plasma cells. Although rituximab was created to treat B-cell lymphoma, its use has widely increased to treat autoimmune diseases. In MG, the benefit of rituximab treatment in MuSK-positive patients seems clear, but a high variability in the results of observational studies and even clinical trials has been reported for AChR-positive patients. Moreover, few evidence has been reported in seronegative MG and juvenile MG and some questions about regimen of administration or monitoring strategies, remains open. In this review, we intend to revise the available literature on this topic and resume the current evidence of effectiveness of Rituximab in MG, with special attention to results on every MG subtype, as well as the administration protocols, monitoring strategies and safety profile of the drug.

B-076 Comparison of Three Methods for the Detection of Antibodies Against Muscle-Specific Kinase

Abstract Background Myasthenia gravis (MG) is a neuromuscular disease characterized by skeletal muscle weakness and fatigue. These symptoms are due to a reduction in synaptic signal transduction caused by autoantibodies against post-synaptic proteins in the neuromuscular junction. Approximately 85% of patients with MG have autoantibodies against acetylcholine receptors (AChR); however, autoantibodies against muscle specific kinase (MuSK) and low-density lipoprotein receptor-related protein 4 (LRP4) may also be found in patients with MG. Detection and identification of these antibodies is important in the diagnosis and treatment of patients under evaluation for MG. MuSK, a transmembrane protein expressed on skeletal muscles, is essential to the formation and maintenance of the neuromuscular junction. Approximately 6% of MG patients have MuSK autoantibodies. Traditionally, radioimmunoprecipitation assays (RIA) have been used to detect MuSK antibodies in patient sera. However, RIA has several limitations, including safety and regulatory concerns associated with using radioactive materials and the short half-life of reagents. Alternatives to RIA, such as enzyme-linked immunosorbent assays (ELISA) and cell-based assays (CBA), do not have the same challenges. Recent studies outside of the USA suggest that cell-based assays may have equal or superior sensitivity than RIA; particularly in the detection of MuSK antibodies in patients previously diagnosed with seronegative MG (MG patients without detectable AChR or MuSK antibodies by RIA). The objective of this study was to compare the performance of two commercially available ELISA and fixed cell-based assay (f-CBA) kits to RIA for the detection of MuSK antibodies. Methods A total of 237 sera were evaluated by RIA, ELISA and/or f-CBA. These sera include 47 MuSK RIA positive sera, 55 MuSK RIA negative sera, 70 self-reported healthy control sera, and 65 sera positive for other neural antibodies associated with MG, Lambert-Eaton Myasthenic Syndrome, paraneoplastic neurologic syndromes, or autoimmune encephalitis. Results Both f-CBA and ELISA demonstrated 100% specificity for MuSK antibodies in sera from self-reported healthy controls and sera from patients positive for other antibodies. Forty-seven sera tested positive for anti-MuSK antibodies by RIA; of those 47 sera, 7 sera tested negative by ELISA and 5 tested negative by f-CBA kits while the remaining 40 were concordant between ELISA, f-CBA and RIA. The discrepancy between RIA and the commercial kits for ELISA and f-CBA was only observed in low positive sera (0.04–0.21 nmol/L ARUP RIA). Clinical information was not available for discrepant specimens. However, a review of MuSK RIA results for University of Utah patients shows that of 7 patients with an ARUP RIA result of 0.04–0.21 nmol/L, only 1 had symptoms that may possibly be consistent with MG. The remaining 6 low positive patients did not have symptoms consistent with a diagnosis of MG. This may suggest an issue with RIA specificity rather than ELISA and f-CBA sensitivity. However, further studies are needed to confirm this. Conclusion Commercially available ELISA and f-CBA kits offer viable alternatives to traditional RIA for detection of MuSK antibodies.

Eye Muscle MRI in Myasthenia Gravis and Other Neuromuscular Disorders.

MRI of extra-ocular muscles (EOM) in patients with myasthenia gravis (MG) could aid in diagnosis and provide insights in therapy-resistant ophthalmoplegia. We used quantitative MRI to study the EOM in MG, healthy and disease controls, including Graves' ophthalmopathy (GO), oculopharyngeal muscular dystrophy (OPMD) and chronic progressive external ophthalmoplegia (CPEO). Twenty recently diagnosed MG (59±19yrs), nineteen chronic MG (51±16yrs), fourteen seronegative MG (57±9yrs) and sixteen healthy controls (54±13yrs) were included. Six CPEO (49±14yrs), OPMD (62±10yrs) and GO patients (44±12yrs) served as disease controls. We quantified muscle fat fraction (FF), T2water and volume. Eye ductions and gaze deviations were assessed by synoptophore and Hess-charting. Chronic, but not recent onset, MG patients showed volume increases (e.g. superior rectus and levator palpebrae [SR+LPS] 985±155 mm3 compared to 884±269 mm3 for healthy controls, p < 0.05). As expected, in CPEO volume was decreased (e.g. SR+LPS 602±193 mm3, p < 0.0001), and in GO volume was increased (e.g. SR+LPS 1419±457 mm3, p < 0.0001). FF was increased in chronic MG (e.g. medial rectus increased 0.017, p < 0.05). In CPEO and OPMD the FF was more severely increased. The severity of ophthalmoplegia did not correlate with EOM volume in MG, but did in CPEO and OPMD. No differences in T2water were found. We observed small increases in EOM volume and FF in chronic MG compared to healthy controls. Surprisingly, we found no atrophy in MG, even in patients with long-term ophthalmoplegia. This implies that even long-term ophthalmoplegia in MG does not lead to secondary structural myopathic changes precluding functional recovery.

Diagnosis and Management of Seronegative Myasthenia Gravis: Lights and Shadows.

Myasthenia gravis (MG) is an antibody-mediated neuromuscular disease affecting the neuromuscular junction. In most cases, autoantibodies can be detected in the sera of MG patients, thus aiding in diagnosis and allowing for early screening. However, there is a small proportion of patients who have no detectable auto-antibodies, a condition termed "seronegative MG" (SnMG). Several factors contribute to this, including laboratory test inaccuracies, decreased antibody production, immunosuppressive therapy, immunodeficiencies, antigen depletion, and immune-senescence. The diagnosis of SnMG is more challenging and is based on clinical features and neurophysiological tests. The early identification of these patients is needed in order to ensure early treatment and prevent complications. This narrative review aims to examine the latest updates on SnMG, defining the clinical characteristics of affected patients, diagnostic methods, management, and therapeutic scenarios.

Circulating miRNAs drive personalized medicine based on subgroup classification in myasthenia gravis patients.

Myasthenia gravis (MG) is a classic autoimmune neuromuscular disease with strong clinical heterogeneity. The concept of subgroup classification was proposed to guide the precise treatment of MG. Subgroups based on serum antibodies and clinical features include ocular MG, early-onset MG with AchR antibodies, late-onset MG with AchR antibodies, thymoma-associated MG, MuSK-associated MG, LRP4-associated MG, and seronegative MG. However, reliable objective biomarkers are still needed to reflect the individualized response to therapy. MicroRNAs (miRNAs) are small non-coding RNA molecules which can specifically bind to target genes and regulate gene expression at the post-transcriptional level, and then influence celluar biological processes. MiRNAs play an important role in the pathogenesis of autoimmune diseases, including MG. Several studies on circulating miRNAs in MG have been reported. However, there is rare systematic review to summarize the differences of these miRNAs in different subgroups of MG. Here, we summarize the potential role of circulating miRNAs in different subgroups of MG to promote personalized medicine.

N°214 - Clinical and electrophysiological markers of seropositive versus seronegative myasthenia gravis: A Tunisian cohort of 75 patients

N°214 - Clinical and electrophysiological markers of seropositive versus seronegative myasthenia gravis: A Tunisian cohort of 75 patients

Utility of Repetitive Nerve Stimulation in the Diagnosis of Myasthenia Gravis in the Inpatient Setting.

Sensitivity and specificity of Repetitive Nerve Stimulation (RNS) is typically reported from outpatient centers, and we hypothesized that these values might not apply to hospitalized patients with higher grades of weakness. RNS may be helpful in rapidly confirming diagnosis of myasthenia gravis (MG) in the inpatient setting, as results from confirmatory antibody testing are often delayed. We sought to characterize the sensitivity and specificity of RNS in the inpatient setting to assist in the early diagnosis of MG. We performed a retrospective analysis of all adult patients who had inpatient RNS at our center from 2016 to 2021. Inclusion criteria included RNS performed at least at one site and a neurological evaluation which prompted an electrodiagnostic study to evaluate for neuromuscular junction (NMJ) pathology. Descriptive statistics and Fisher exact analysis were performed. Of the 32 identified hospitalized patients, 6 had greater than 10% decrement on slow RNS, confirming NMJ dysfunction. Five were diagnosed with MG, and 1 with Lambert-Eaton myasthenic syndrome. Of the 26 patients with normal RNS, 25 ultimately had alternative causes of weakness. One was later diagnosed as seronegative MG based on clinical improvement with acetylcholinesterase inhibitors. In our inpatient population, the overall sensitivity and specificity of RNS were 83.3% and 96.2% respectively. There was a statistically significant association between a positive RNS and diagnosis of MG (P = .0002). RNS is a highly sensitive and specific test for the diagnosis of MG in an inpatient setting, and these results are likely more rapidly available compared to antibody testing.

Triple M Syndrome with Triple Seronegative Myasthenia Gravis presenting as a Non-ST Elevation Myocardial Infarction (P1-8.002)

<h3>Objective:</h3> N/A <h3>Background:</h3> Immune checkpoint inhibitors hinder different receptors in the immune system that maintain immunologic self-tolerance. Despite their efficacy, multiple reports of immune related adverse events exist. 1–3% of these cases are neurological. There is no clear consensus on how to treat this patient population. <h3>Design/Methods:</h3> We present a case of myocarditis, myositis and triple seronegative myasthenia gravis overlap syndrome secondary to PD-1 inhibitor. <h3>Results:</h3> 75-year-old male with a history of lung cancer and severe coronary artery disease who presented for chest pain and dyspnea. He had recently been started on gabapentin for chemotherapy related neuropathy. Due to recurrent lung cancer he was started on a new PD-1 inhibitor. On admission, he had elevated troponins. Emergency cardiac catheterization was negative for new coronary artery disease. Echocardiogram showed septal and LV wall hypokinesis, patient was admitted as NSTEMI. On physical exam, he had neck muscle weakness with drooping head sign, right eye ptosis, and proximal limb muscle weakness with fatigability of all extremities. Ice pack test done at the bedside showed improvement in right eye ptosis and neck drop. Anti-Ach Binding, Block and Modulating, Anti-Musk and Anti-LRP4 antibodies were negative. Due to suspicion of triple M syndrome he was treated IV Methylprednisolone and Pyridostigmine which stabilized his weakness. His dyspnea continued to worsen despite steroid therapy and he was started on IVIG. After 5 doses he significantly improved and was discharged to an acute rehabilitation facility. <h3>Conclusions:</h3> ICIs associated myocarditis can occur in 1% of patients. Up to 10% of these patients can have overlapping myasthenia gravis and myositis. 10% of patients with this syndrome can have seronegative myasthenia gravis. There are no guidelines adressing the correct treatment approach for this syndrome. In our case, gabapentin possibly precipitated the myasthenic symptoms and treatment with Corticosteroids and IVIG resolved the patient’s symptomatology. <b>Disclosure:</b> Dr. Carranza-Renteria has nothing to disclose. Dr. Mattner has nothing to disclose. Ms. Sial has nothing to disclose. Dr. Babici has nothing to disclose. Dr. Dragomir has nothing to disclose. Dr. Rodriguez-Hernandez has nothing to disclose. Dr. Hammond has nothing to disclose.

Rare case of double seronegative ocular myasthenia gravis and non-functional pituitary macroadenoma

Chronic autoimmune neuromuscular disorder known as Myasthenia Gravis (MG). The relationship of myasthenia gravis with pituitary adenomas is relatively uncommon, despite the fact that it is widely known that people with the condition have a higher prevalence of other autoimmune diseases. Here, we describe the case of a 45-year-old Indian man who had complained of severe cephalgia, associated with ocular pain, dizziness, diplopia, ptosis of the unilateral right eye. Although he has a history of severe headaches that started prior to 3 months, his complaints became more obvious at the end of the day. An MRI of the brain revealed an increased pituitary gland that measured 13.7 × 15.5 x 16. 9 mm. Furthermore, post admission histological examinations supported the diagnosis of a double seronegative ocular myasthenia gravis and non-functional pituitary macroadenoma. Following treatment, it was discovered that Pyridostigmin and Prednisolone considerably reduced his myasthenia symptoms. Finally, it should be noted that pituitary tumours are one potential underlying cause of headache in myasthenic patients.

AMPA and NMDA receptor antibody autoimmune encephalitis preceded by ocular myasthenia gravis: a case report

Backgroundα-Amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) and N-methyl-D-aspartate (NMDA) receptors mediate excitatory neurotransmission in the brain and may be targeted by autoantibodies, leading to autoimmune synaptic encephalitis (AE). AE can be associated with other autoimmune diseases. However, the cooccurrence of anti-AMPA and NMDA receptor AE together with myasthenia gravis (MG) is unusual.Case presentationA 24-year-old previously healthy male presented with seronegative ocular MG, the diagnosis of which was supported by single-fiber electrophysiology findings. Three months later, he developed AE, initially being positive for AMPA receptor antibodies and subsequently for NMDA receptor antibodies. No underlying malignancy was found. In response to aggressive immunosuppressive treatment, he recovered (modified Rankin Scale (mRS) score change from 5 to 1). Despite some cognitive problems at the 1-year follow-up, which were not revealed using the mRS, he was able to return to his studies.ConclusionsAE may coexist with other autoimmune disorders. Patients with seronegative MG, including ocular MG, may develop autoimmune encephalitis with more than one cell-surface antibody.

Complement activation profiles in anti-acetylcholine receptor positive myasthenia gravis.

Complement component 5 (C5) targeting therapies are clinically beneficial in patients with acetylcholine receptor antibody+ (AChR-Ab+ ) generalized myasthenia gravis (MG). That clearly implicates antibody-mediated complement activation in MG pathogenesis. Here, classical and alternative complement pathways were profiled in patients from different MG subgroups. In a case-control study, concentrations of C3a, C5a and sC5b9 were simultaneously quantified, indicating general activation of the complement system, whether via the classical and lectin pathways (C4a) or the alternative pathway (factors Ba and Bb) in MG patients with AChR or muscle-specific kinase antibodies (MuSK-Abs) or seronegative MG compared to healthy donors. Treatment-naïve patients with AChR-Ab+ MG showed substantially increased plasma levels of cleaved complement components, indicating activation of the classical and alternative as well as the terminal complement pathways. These increases were still present in a validation cohort of AChR-Ab+ patients under standard immunosuppressive therapies; notably, they were not evident in patients with MuSK-Abs or seronegative MG. Neither clinical severity parameters (at the time of sampling or 1 year later) nor anti-AChR titres correlated significantly with activated complement levels. Markers indicative of complement activation are prominently increased in patients with AChR-Ab MG despite standard immunosuppressive therapies. Complement inhibition proximal to C5 cleavage should be explored for its potential therapeutic benefits in AChR-Ab+ MG.

Chronic mimics of myasthenia gravis: a retrospective case series

Myasthenia gravis often presents a diagnostic challenge and may be misdiagnosed, particularly in seronegative disease with active symptoms. We retrospectively evaluated 61 patients following the introduction of single fibre electromyography at our service, and identified 8 mimics which had been inappropriately diagnosed and treated as refractory myasthenia gravis. 6 of these were seronegative, but two had positive acetylcholine receptor (AChR) antibodies. The final diagnoses included one case each of chronic progressive external ophthalmoplegia, chronic ptosis, oculopharyngeal muscular dystrophy, and an undifferentiated disorder suspicious for either a mitochondrial cytopathy or low-grade myositis. Four were diagnosed with functional neurological disorder, one of which had a superimposed thyroid myopathy and orbitopathy. We found the average duration of misdiagnosis was 9 years (SD±5.2, median 11 years), and patients were often exposed to years of unnecessary treatment. All patients had received anticholinesterase therapy, three had immunotherapy, and three surgical interventions were performed including two thymectomies. We found myasthenic mimics should be suspected in disease that is static and treatment refractory, and functional mimics in disease with frequent flares. Thorough neurophysiologic assessment is important, particularly when making a diagnosis of seronegative myasthenia gravis.

Serum neurofilament light chain in myasthenia gravis subgroups: An exploratory cohort and case-Control study.

This study aimed to evaluate the association of neurofilament light chain (Nfl) with neuromuscular destruction and disease severity in the serum of patients with myasthenia gravis (MG). Sera from 134 patients with MG with varying degrees of disease severity and autoantibody (Abs) status were analyzed and compared to controls in a cross-sectional design. Prospectively, we additionally measured serum NfL (sNfl) levels in patients with MG longitudinally for up to 3 years. Based on linear regression, differences between patients and controls were assessed. With correlation coefficients and mixed linear regression, the association among sNfl levels, socio-demographics, disease activity (Quantitative Myasthenia Gravis (QMG) score and Myasthenia Gravis Activities of Daily Living (MG-ADL) scale), Abs-status (acetylcholine receptor antibody (AChR-Abs), muscle-specific receptor tyrosine kinase antibody (MuSK-Abs), lipoprotein-related protein 4 (LRP4), and seronegative), Abs titer, treatment regime (pyridostigmine, steroids, and immunosuppressive therapies), and thymectomy were investigated. sNfl levels were higher in patients with MG compared to controls (median: 11.2 vs. 7.88), where sNfl levels were highest in anti-AChR-Abs positive patients (median 12.6), followed by anti-MuSK-Abs positive, anti-LRP4-Abs positive, and seronegative patients. Adjusting for age and sex, sNfl levels of patients with MG were on average 35% higher compared to controls (35.1, 95% CI: 8.4;68.3) and highest for patients with seronegative MG (44.35; 95% CI 16.47; 78.90). We found no relevant relationship between individual changes in sNfl and changes in QMG and MG-ADL scores. sNfl levels are higher in patients with MG than in controls but were not consistently associated with clinical severity. Thus, sNfl is not a suitable biomarker to monitor individual disease progression in patients with MG.

Autoantibody detection by a live cell-based assay in conventionally antibody-tested triple seronegative Myasthenia gravis

Autoantibody testing is the mainstay in confirming the diagnosis of autoimmune myasthenia gravis (MG). However, in approximately 15% of patients, antibody testing in clinical routine remains negative (seronegative MG). This study aimed at assessing the prevalence of “clustered” AChR- and MuSK- and LRP4- autoantibodies using a live cell-based assay in a large German cohort of seronegative myasthenia gravis (SNMG) patients. A total of 67 SNMG patients were included. Clustered AChR-ab were identified in 4.5% (n = 3) of patients. Two out of the three patients showed binding to the adult AchR as well as the fetal AchR. None of the patients was positive for MuSK- or LRP4-autoantibodies. There were no differences in clinical characteristics between the patients with and without clustered AChR-ab detection. Comparison of clinical data of our cohort with clinical data from the nationwide Myasthenia gravis registry showed broad similarities between seronegative MG patients of both cohorts.

Case Report: The first reported case of pulmonary alveolar proteinosis with myasthenia gravis in a 27-year-old patient

Background: Pulmonary alveolar proteinosis is a very rare diffuse lung disease characterized by the accumulation of amorphous and periodic acid Schiff-positive lipoproteinaceous material in the alveolar spaces due to impaired surfactant clearance by alveolar macrophages. Three main types were identified: Autoimmune, secondary and congenital. Pulmonary alveolar proteinosis has been previously reported to be associated with several systemic auto-immune diseases. Accordingly, we present the first case report of pulmonary alveolar proteinosis associated with myasthenia gravis. Case: A 27-year-old female patient, ex-smoker, developed a dyspnea on exertion in 2020. The chest X-ray detected diffuse symmetric alveolar opacities. Pulmonary infection was ruled out, particularly COVID-19 infection. The chest scan revealed the “crazy paving” pattern. The bronchoalveolar lavage showed a rosy liquid with granular acellular eosinophilic material Periodic acid-Schiff positive. According to the lung biopsy results, she was diagnosed with pulmonary alveolar proteinosis. The granulocyte macrophage colony-stimulating factor autoantibodies were negative. Nine months later, she was diagnosed with bulbar seronegative myasthenia gravis, confirmed with the electroneuromyography with repetitive nerve stimulation showing significant amplitude decrement of the trapezius and spinal muscles. She was treated with pyridostigmine, oral corticosteroids and azathioprine. Given the worsening respiratory condition of the patient, a bilateral whole lung lavage was performed with a partial resolution of symptoms. Thus, this previously unreported association was treated successfully with rituximab, including improvement of dyspnea, diplopia and muscle fatigability at six months of follow-up. Conclusions: This case emphasizes on the possible association of auto-immune disease to PAP, which could worsen the disease course, as the specific treatment does not exist yet. Hence, further studies are needed to establish clear-cut guidelines for PAP management, particularly when associated to auto-immune diseases.

Clinical pitfalls and serological diagnostics of MuSK myasthenia gravis

BackgroundWe aimed to evaluate the diagnostic accuracy of enzyme-linked immunosorbent assay (ELISA) for anti-muscle specific tyrosine kinase (MuSK) antibody (Ab) in a large cohort of anti-acetylcholine receptor (AChR) Ab-negative generalized myasthenia gravis (MG), and also to investigate clinical contexts for the diagnosis of MuSK MG.MethodsA retrospective study of 160 patients with a clinical suspicion of AChR Ab-negative generalized MG was performed. The serum samples were tested for anti-clustered AChR Ab by cell-based assay (CBA), anti-MuSK Ab by ELISA, CBA and/or radioimmunoprecipitation assay (RIPA). Clinical data were compared between anti-MuSK Ab-positive MG and double seronegative (AChR and MuSK) MG groups.ResultsAfter excluding non-MG and clustered AChR Ab-positive patients, we identified 89 patients as a cohort of AChR Ab-negative generalized MG. Anti-MuSK Ab was positive by ELISA in 22 (24.7%) patients. While CBA identified five additional anti-MuSK Ab-positive patients, the results of ELISA were mostly consistent with CBA and RIPA with Cohen’s kappa of 0.80 and 0.90, respectively (p < 0.001). The most frequent differential diagnosis was motor neuron disease particularly of bulbar onset which showed remarkably overlapping clinical and electrophysiological features with MuSK MG at presentation.ConclusionWhile confirming the highest sensitivity of CBA for detecting anti-MuSK Ab, our results highlight the clinical pitfalls in making a diagnosis of MuSK MG and may support a diagnostic utility of MuSK-ELISA in clinical practice.