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.

[Peripheral Neuropathy and Muscle Disorders as Immune-Related Adverse Events].

Neurological immune-related adverse events (irAEs) associated with cancer treatment with immune checkpoint inhibitors (ICI) present diverse clinical characteristics. Neurological irAEs affect the peripheral nervous system and muscles more than they affect the central nervous system. Among the various subsets of peripheral neuropathies, polyradiculoneuropathy, which includes Guillain-Barre syndrome and chronic inflammatory demyelinating polyneuropathy, stands out as the most severe form, leading to significant muscle weakness. ICIs can induce dysautonomia, including autoimmune autonomic ganglionopathy. Autonomic neuropathy represents a neurological irAE. Neurological irAEs of neuromuscular junctions include myasthenia gravis (MG) and Lambert-Eaton myasthenic syndrome (LEMS). Diagnosing MG or myositis independently can be challenging when they occur as irAEs. Myocarditis is sometimes observed as an irAE in patients with MG and can cause both severe heart failure and lethal arrhythmias, resulting in fatal outcomes. Anti-Kv1.4 antibodies are biomarkers of the severe form of MG and myocarditis. The administration of ICI in patients with small cell lung cancer increases the risk of LEMS. The distinction between LEMS is an irAE or a manifestation of paraneoplastic neurological syndrome is unclear as both conditions share common immunological mechanisms.

Real-world experience with eculizumab and switching to ravulizumab for generalized myasthenia gravis.

OBJECTIVE: Eculizumab and ravulizumab are complement protein C5 inhibitors, showing efficacy and tolerability for patients with anti-acetylcholine receptor-positive (AChR+) generalized myasthenia gravis (gMG) in phase 3 clinical trials and subsequent analyses. The purpose of the present study was to evaluate the clinical significance of eculizumab and switching to ravulizumab for refractory AChR+ gMG patients in the real-world experience. METHODS: Among the database of Japan MG registry survey 2021, we studied AChR+ gMG patients who received eculizumab. We also evaluated these patients who switched from eculizumab to ravulizumab. Responder was defined as an improvement of at least 3 points in MG-ADL. We performed a questionnaire of preference between eculizumab and ravulizumab. RESULTS: Among 1,106 patients with AChR+ gMG, 36 patients (3%) received eculizumab (female 78%, mean age 56.0 years). Eculizumab was preferentially used in severe and refractory MG patients. The duration of eculizumab treatment was 35 months on average. MG-ADL improved from 9.4 ± 4.9 to 5.9 ± 5.1, and 25 (70%) of the 36 gMG patients were responders. Postintervention status was markedly improved after the eculizumab treatment. Of 13 patients who did not continue eculizumab, 6 showed insufficiencies. Early onset MG was most effective. However, 15 patients switching from eculizumab to ravulizumab kept favorable response and tolerability. Questionnaire surveys showed preference for ravulizumab over eculizumab. INTERPRETATION: Eculizumab and switching to ravulizumab showed to be effective for refractory AChR+ gMG patients in clinical settings.

Taste disorders and alopecia in myasthenia gravis.

BACKGROUND: Non-motor symptoms in myasthenia gravis (MG) are rarely confirmed. Although there are some small cohort studies, a large-systemic survey has not yet been performed. METHODS: We investigated the incidence and clinical characteristics of patients with MG who had taste disorders and alopecia using data of 1710 patients with MG enrolled in the Japan MG Registry 2021. RESULTS: Among them, 104 (6.1%) out of 1692 patients and 138 (8.2%) out of 1688 patients had histories of taste disorders and alopecia, respectively. Among the patients with MG, taste disorders were significantly more common in women, those with severe symptoms, refractory MG, or thymoma-associated MG, and were less common in those with ocular MG. The taste disorders often occurred after the onset of MG and often responded to MG treatments. Alopecia was more common in MG patients with a history of bulbar palsy and thymoma, and it often occurred before the onset of MG and sometimes responded to MG treatments. Multivariate logistic regression analysis revealed taste disturbance was associated with worst quantitative MG score and thymoma-associated MG; and alopecia was associated with thymoma-associated MG. CONCLUSION: Clinicians should be aware of the non-motor symptoms in MG, especially in patients with severe myasthenic symptoms and thymoma-associated MG.

Pathologic Features of Anti-Ku Myositis.

OBJECTIVE: Characteristics of myositis with anti-Ku antibodies are poorly understood. The purpose of this study was to elucidate the pathologic features of myositis associated with anti-Ku antibodies, compared with immune-mediated necrotizing myopathy (IMNM) with anti-signal recognition particle (SRP) and anti-3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCR) antibodies, in muscle biopsy-oriented registration cohorts in Japan and Germany. METHODS: We performed a retrospective pathology review of patients with anti-Ku myositis samples diagnosed in the Japanese and German cohorts. We evaluated histologic features and performed HLA phenotyping. RESULTS: Fifty biopsied muscle samples in the Japanese cohort and 10 in the German cohort were obtained. After exclusion of myositis-specific autoantibodies or other autoimmune connective tissue diseases, 26 samples (43%) of anti-Ku antibody-positive myositis were analyzed. All the samples shared some common features with IMNM, whereas they showed expression of MHC class II and clusters of perivascular inflammatory cells more frequently than the anti-SRP/HMGCR IMNM samples (71% vs 7%/16%; p < 0.005/<0.005; 64% vs 0%/0%; p < 0.005/<0.005). Anti-Ku myositis biopsies could be divided into 2 subgroups based on the extent of necrosis and regeneration. The group with more abundant necrosis and regeneration showed a higher frequency of MHC class II expression and perivascular inflammatory cell clusters. HLA phenotyping in the 44 available patients showed possible associations of HLA-DRB1*03:01, HLA-DRB1*11:01, and HLA-DQB1*03:01 (p = 0.0045, 0.019, and 0.027; odds ratio [OR] 50.2, 4.6, and 2.8; 95% CI 2.6-2942.1, 1.1-14.5, and 1.0-7.0) in the group with less conspicuous necrosis and regeneration. On the contrary, in the group of more abundant necrosis and regeneration, the allele frequencies of HLA-A*24:02, HLA-B*52:01, HLA-C*12:02, and HLA-DRB1*15:02 were lower than those of healthy controls (p = 0.0036, 0.027, 0.016, and 0.026; OR = 0.27, 0, 0, and 0; 95% CI 0.1-0.7, 0-0.8, 0-0.8, and 0-0.8). However, these HLA associations did not remain significant after statistical correction for multiple testing. DISCUSSION: While anti-Ku myositis shows necrotizing myopathy features, they can be distinguished from anti-SRP/HMGCR IMNM by their MHC class II expression and clusters of perivascular inflammatory cells. The HLA analyses suggest that anti-Ku myositis may have different subsets associated with myopathologic subgroups.

Therapeutic Responses to Efgartigimod for Generalized Myasthenia Gravis in Japan.

Background and Objectives: Efgartigimod, which has been well tolerated and efficacious in individuals with generalized myasthenia gravis (MG), is available in Japan not only for the treatment of anti-acetylcholine receptor-positive (AChR+) but also anti-muscle-specific receptor tyrosine kinase (MuSK+) and seronegative generalized MG. We report details of the use of efgartigimod for generalized MG in clinical practice in Japan. Methods: We included patients with generalized MG in the 2021 survey of Japan Myasthenia Gravis Registry (JAMG-R) study group who received an initial cycle of efgartigimod between May and September 2022. We defined "responders" as patients who achieved a score ≥2 points for MG activities of daily living (MG-ADL) in the first treatment cycle. The MG composite and the Revised scale of the 15-item Myasthenia Gravis-Quality of Life scale (MG-QOL15-r) were also evaluated. Results: Of 1,343 JAMG-R patients, 36 (2.7%) started efgartigimod (female 68%, age 53 years). Their serologic profiles were as follows: AChR+, n = 19 (53%); MuSK+, n = 6 (17%); and seronegative, n = 11 (31%). Twenty-six patients (72%) had refractory MG. There were 81 cycles of efgartigimod during the 26-week observation in 34 patients (average, 2.4 cycles). The mean interval between cycles was 5.9 weeks. A continuous 4-weekly infusion of efgartigimod was performed in 65 (80%) of 81 cycles. In the first cycle, the MG-ADL score of the 34 patients decreased significantly from 10.5 ± 4.3 to 6.9 ± 5.1 (p = 0.003). Similarly, the mean MG composite and MG-QOL15-r decreased from 18.4 ± 13.6 to 11.8 ± 9.6 (p = 0.004) and from 19.2 ± 6.3 to 14.2 ± 8.3 (p = 0.007), respectively. Twenty-one (62%) patients were responders. Therapeutic responses were observed in the subsequent cycles. The duration of effectiveness of efgartigimod was varied among the responders; 4 responders had only a single effective cycle. Significant improvement was observed in the MuSK+ patients. Prednisolone dose of 7 patients was reduced. Our examination of the patients' postintervention status revealed that 6 patients achieved minimal manifestations. COVID-19 occurred in 5 patients. We failed to detect clinical or laboratory findings associated with responders. Discussion: Efgartigimod can be considered for the treatment of patients with generalized MG who do not achieve minimal manifestations, with a broad flexibility of patient selection and treatment schedules.

Efficacy of ravulizumab in patients with generalized myasthenia gravis by time from diagnosis: A post hoc subgroup analysis of the CHAMPION MG study.

INTRODUCTION/AIMS: The CHAMPION MG study demonstrated that ravulizumab significantly improved Myasthenia Gravis-Activities of Daily Living (MG-ADL) and Quantitative Myasthenia Gravis (QMG) total scores versus placebo in adults with acetylcholine receptor antibody-positive generalized myasthenia gravis (AChR+ gMG). This post hoc analysis aimed to assess these outcomes by time from MG diagnosis. METHODS: Changes from baseline to week 26 in MG-ADL and QMG total scores were analyzed by time from MG diagnosis to study entry (≤2 vs. >2 years). Within each subgroup, least-squares (LS) mean changes for ravulizumab and placebo were compared using mixed models for repeated measures. RESULTS: In ravulizumab-treated patients, differences in LS mean (standard error of the mean) changes from baseline to week 26 were not statistically significant in the ≤2-years subgroup versus the >2-years subgroup for MG-ADL (-4.3 [0.70] vs. -2.9 [0.37]; p = .0511) or QMG (-4.3 [0.94] vs. -2.5 [0.50]; p = .0822) scores. No clear trends were observed in the placebo group. LS mean changes from baseline were significantly greater for ravulizumab versus placebo in both the ≤2 and >2 years from diagnosis subgroups for MG-ADL and QMG scores (all p < .05). The difference in treatment effect between the ≤2-years and >2-years subgroups was not statistically significant. No clinically meaningful between-subgroup differences in treatment-emergent adverse events were observed in ravulizumab-treated patients. DISCUSSION: Ravulizumab treatment improved clinical outcomes for patients with AChR+ gMG regardless of time from diagnosis. A numerical trend was observed favoring greater treatment effect with earlier versus later treatment after diagnosis. Further studies are required for confirmation.

Clinicopathological predictors of postoperative long-term myasthenic status in resected thymoma with myasthenia gravis.

PURPOSE: Surgical patients with thymoma and myasthenia gravis (MG) must have their MG status and oncological outcomes critically monitored. We aimed to identify clinicopathological predictors of the postoperative MG status. METHODS: We conducted a retrospective review of 40 consecutive surgical patients with MG-related thymomas between 2002 and 2020. The quantitative myasthenia gravis score (QMGS) and Myasthenia Gravis Foundation of America post-intervention status (MGFA-PIS) were used to evaluate postoperative MG status. RESULTS: All patients underwent extended total thymectomy. The most common WHO type was type B2 (32%), while 65% of patients had type B1-B3 and 35% had type A-AB thymomas. Eleven patients (28%) achieved controlled MG status in MGFA-PIS 6 months after surgery. This controlled status was observed more frequently in type A-AB than in B1-B3 (57% vs. 12%, p = 0.007). In a multivariate analysis, WHO type (A-AB or B1-B3) was an independent predictor of worsening episodes of MG based on the QMGS (Type B1-B3, hazard ratio: 3.23, 95% confidence interval: 1.12-9.25). At the last follow-up, 23 patients (58%) achieved controlled MG status. The 5-year overall survival rate of all patients was 93.7%. CONCLUSION: The WHO type of thymoma is an informative predictor of postoperative MG status in patients with MG-related thymoma.

[Clinical Features of Myasthenia Gravis as an Immune-related Adverse Event].

Neurological and muscular immune-related adverse events (irAEs) associated with cancer treatment using immune checkpoint inhibitors (ICIs) may show a diverse clinical presentation. Myasthenia gravis (MG) represents a serious irAE associated with the aforementioned therapy. Recent studies have discussed the clinical features of MG that occurs as an irAE (irAE-MG). The incidence of irAE-MG is estimated to be 1%. This complication occurs during the early phase of ICI treatment and rapidly worsens, resulting in severe bulbar muscle involvement and myasthenic crisis and significantly elevated serum creatine kinase levels. MG and myositis, which may occur concomitantly as irAEs are often indistinguishable. Myocarditis is occasionally observed in patients with irAE-MG and can cause severe heart failure and lethal arrhythmias, with a fatal outcome. Kv1.4 antibodies serve as biomarkers of severe irAE-MG and myocarditis. Immunotherapy with corticosteroids is effective for management of irAE-MG and should be initiated promptly. Collaboration between consulting neurologists is necessary for safe management of cancer immunotherapy.

Serious Bacterial Infections Associated with Eculizumab: A Pharmacovigilance Study.

Objective Molecular-targeted agents, including eculizumab and rituximab, are considered treatment options for refractory myasthenia gravis (MG), but bacterial infections can occur as serious adverse events when using these agents. The present study elucidated the relative risks of bacterial infections associated with eculizumab and rituximab using a pharmacovigilance database. Methods We analyzed eculizumab- and rituximab-associated adverse events reported between 2007 and 2021 in the US Food and Drug Administration Adverse Event Reporting System (FAERS) and herein report a refractory MG patient who developed streptococcal toxic shock syndrome during eculizumab treatment. Patients We evaluated a 74-year-old Japanese woman with refractory MG who developed severe bacteremia after receiving eculizumab. Results A total of 44,215 and 108,485 adverse events were reported with eculizumab and rituximab, respectively, from among 13,742,321 individual case safety reports in the FAERS database after data cleaning. We found a strong association between eculizumab and Neisseria infections. In contrast, we found only one case of meningococcal meningitis treated with rituximab. Both eculizumab and rituximab were weakly associated with streptococcal infections. Two cases of streptococcal toxic shock syndrome were associated with rituximab. Conclusion Careful monitoring of serious bacterial infections associated with eculizumab treatment is warranted.

Clinical features and outcomes of patients with muscle-specific kinase antibody-positive myasthenia gravis in Japan.

This study included 51 patients with muscle-specific kinase antibody-positive myasthenia gravis (MuSK-MG) from a Japanese multicenter survey to examine clinical features and outcomes. Median onset age was 37 years and female predominance was observed. All patients developed generalized symptoms and almost all (50/51) patients had bulbar symptoms. About half of the patients met the criteria for refractory MG. The refractory group had a lower age of onset, higher severity scores, and higher maximum daily doses of oral prednisolone compared to the nonrefractory group. The outcomes for MuSK-MG patients in Japan are not favorable, indicating the need for more aggressive treatment.

Association Between HLA Alleles and Autoantibodies in Dermatomyositis Defined by Sarcoplasmic Expression of Myxovirus Resistance Protein A.

OBJECTIVE: The diagnosis in the studies analyzing HLA of dermatomyositis (DM) was based on a combined clinical category of polymyositis/DM. This retrospective study investigated the associations of HLA with 5 DM-specific autoantibodies in Japanese patients diagnosed by muscle pathology. METHODS: We diagnosed Japanese patients with DM based on sarcoplasmic expression of myxovirus resistance protein A. These patients underwent investigation for 5 DM-specific autoantibodies and HLA genotyping. RESULTS: Of 175 patients (83 males and 92 females; range 1-86 yrs; mean 46 yrs), 173 (98.9%) had 1 of the 5 autoantibodies. Seven alleles-A*02:07, B*46:01, DRB1*04:07, DRB1*07:01, DRB1*08:03, DQB1*06:01, and DPB1*02:02-were more frequently detected in the patients with DM than healthy controls, but these associations were not significant after multiple testing correction. Stratifying by DM-specific autoantibodies, we found the associations of 6 already known and 7 new alleles-B*48:01, B*52:01, C*12:02, DRB1*04:05, DRB1*15:02, DPB1*05:01, and DPB1*09:01-with subsets of DM. Moreover, significant associations of 5 alleles with antinucleosome remodeling deacetylase complex (Mi-2) remained after multiple testing correction. In particular, the DRB1*04:07 (odds ratio [OR 28.9]; corrected P = 2.7 × 10-6) and DQB1*06:01 (OR 4.0; corrected P = 1.6 × 10-4) alleles were significantly more prevalent in patients with anti-Mi-2 antibody than in controls. CONCLUSION: This study demonstrates DM-specific autoantibodies defined immunogenetic subsets of DM.

Overlap syndrome with antibodies against multiple transfer-RNA components presenting antisynthetase syndrome.

Overlap syndrome is a clinical entity of myositis concomitant with one or more collagen diseases such as systemic lupus erythematosus, systemic sclerosis, and/or rheumatoid arthritis. It is not evident whether the myopathology of overlap syndrome is disease-specific or categorizes one of the four major subsets: inclusion body myositis, immune-mediated necrotizing myopathy, dermatomyositis, and antisynthetase syndrome. We report a patient with overlap syndrome who exhibited autoantibodies against multiple transfer-RNA components by RNA immunoprecipitation, suggesting antisynthetase syndrome. A 64-year-old woman developed systemic lupus erythematosus, systemic sclerosis, and myositis. Muscle biopsy showed perifascicular necrosis and perimysial alkaline phosphatase positivity, suggesting antisynthetase syndrome. Enzyme-linked immunosorbent assay was negative for autoantibodies to aminoacyl transfer-RNA synthetase, whereas RNA immunoprecipitation revealed a novel antibody to multiple transfer-RNA components. Although the myopathology of overlap syndrome may be diagnosed as any one of various subsets, this case suggests that the myopathological features of overlap syndrome may include antisynthetase syndrome.

Muscle pathology of antisynthetase syndrome according to antibody subtypes.

Identification of antisynthetase syndrome (ASS) could be challenging due to inaccessibility and technical difficulty of the serology test for the less common non-Jo-1 antibodies. This study aimed to describe ASS antibody-specific myopathology and evaluate the diagnostic utility of myofiber HLA-DR expression. We reviewed 212 ASS muscle biopsies and compared myopathologic features among subtypes. Additionally, we compared their HLA-DR staining pattern with 602 non-ASS myositis and 140 genetically confirmed myopathies known to have an inflammatory component. We used t-test and Fisher's exact for comparisons and used sensitivity, specificity, positive and negative predictive values to assess the utility of HLA-DR expression for ASS diagnosis. RNAseq performed from a subset of myositis cases and histologically normal muscle biopsies was used to evaluate interferon (IFN)-signaling pathway-related genes. Anti-OJ ASS showed prominent myopathology with higher scores in muscle fiber (4.6 ± 2.0 vs. 2.8 ± 1.8, p = 0.001) and inflammatory domains (6.8 ± 3.2 vs. 4.5 ± 2.9, p  = 0.006) than non-OJ ASS. HLA-DR expression and IFN-γ-related genes upregulation were prominent in ASS and inclusion body myositis (IBM). When dermatomyositis and IBM were excluded, HLA-DR expression was 95.4% specific and 61.2% sensitive for ASS with a positive predictive value of 85.9% and a negative predictive value of 84.2%; perifascicular HLA-DR pattern is common in anti-Jo-1 ASS than non-Jo-1 ASS (63.1% vs. 5.1%, p < 0.0001). In the appropriate clinicopathological context, myofiber HLA-DR expression help support ASS diagnosis. The presence of HLA-DR expression suggests involvement of IFN-γ in the pathogenesis of ASS, though the detailed mechanisms have yet to be elucidated.

Dysautonomia associated with immune checkpoint inhibitors.

OBJECTIVE: The purpose of this study is to report the clinical characteristics of dysautonomia associated with immune checkpoint inhibitors (ICIs). METHODS: We reported two patients with autoimmune autonomic ganglionopathy (AAG) occurring as immune-related adverse events (irAEs). We also performed a review of previous case reports presenting dysautonomia during ICI therapy. Moreover, we conducted pharmacovigilance analyses using the US Food and Drug Administration Adverse Events Reporting System (FAERS) to investigate dysautonomia associated with ICI. RESULTS: Two patients in our care developed both AAG and autoimmune encephalitis following ICI therapy for lung cancers. We comprehensively reviewed 13 published cases (M:F = 11:2, mean onset age of 53 years) with ICI-associated dysautonomia including AAG (n = 3) and autonomic neuropathy (n = 10). Of these, ICI monotherapy was performed in seven and combination ICI use in six. In 6 of 13 patients, dysautonomia appeared within one month after the start of ICIs. Orthostatic hypotension was observed in 7 and urinary incontinence or retention in five. All patients except three showed gastrointestinal symptoms. Anti-ganglionic acetylcholine receptor antibodies were undetectable. All but two patients received immune-modulating therapy. Immuno-modulating therapy was effective in three patients with AAG and two patients with autonomic neuropathy, but ineffective in the others. Five patients died, of either the neurological irAE (n = 3) or cancer (n = 2). The pharmacovigilance analyses using FAERS showed that ipilimumab monotherapy and the combination of nivolumab and ipilimumab constituted significant risks for developing dysautonomia, consistent with the review of literature. CONCLUSION: ICIs can cause dysautonomia including AAG, and autonomic neuropathy is a neurological irAE.

Impact of Early Treatment with Intravenous High-Dose Methylprednisolone for Ocular Myasthenia Gravis.

The efficacy of intravenous high-dose methylprednisolone (IVMP) in ocular myasthenia gravis (MG) has not been fully established. This study aimed to elucidate the effects of early intervention with IVMP for achieving the therapeutic targets (minimal manifestations [MM] or MM or better status with prednisolone ≤ 5 mg/day [MM5mg]) in ocular MG. In this observational study, we included a total of 1710 consecutive patients with MG enrolled in the Japan MG Registry in 2021. Of these, 204 patients with ocular MG who received immunotherapy were analyzed. The clinical course and time to first achieve MM or MM5mg after starting immunotherapy were compared between the early IVMP group (treated with IVMP within 3 months of treatment initiation) and the non-early IVMP group. Despite having greater clinical severity before immunotherapy and lower oral prednisolone doses throughout the course, the early IVMP group (n = 55) showed a higher rate of achievement of MM (P = 0.0040, log-rank test; hazard ratio 1.58, 95% confidence interval [CI] 1.13-2.20, P < 0.0001) and MM5mg (P = 0.0005, log-rank test; hazard ratio 1.78, 95% CI 1.27-2.51, P < 0.0001) compared with the non-early IVMP group (n = 149). In conclusion, an early intervention with IVMP is likely to increase the probability of achieving a better long-term outcome and reducing the total dose of corticosteroids in ocular MG.

Effectiveness of early cycles of fast-acting treatment in generalised myasthenia gravis.

BACKGROUND: Early fast-acting treatment (EFT) is the aggressive use of fast-acting therapies such as plasmapheresis, intravenous immunoglobulin and/or intravenous high-dose methylprednisolone (IVMP) from the early phases of treatment. EFT is reportedly beneficial for early achievement of minimal manifestations (MM) or better status with ≤5 mg/day prednisolone (MM5mg), a practical therapeutic target for myasthenia gravis (MG). OBJECTIVE: The current study aimed to clarify which specific EFT regimen is efficacious and the patient characteristics that confer sensitivity to EFT. METHODS: We recruited a total of 1710 consecutive patients with MG who enrolled in the Japan MG Registry for this large-cohort study. Among them, 1066 with generalised MG who had received immunotherapy were analysed. Prognostic background factors were matched in a 1:1 ratio using propensity score matching analysis between patients treated with EFT (n=350) and those treated without EFT (n=350). The clinical course and time to first achieve MM5mg after starting immunotherapy was analysed in relation to treatment combinations and patient characteristics. RESULTS: Kaplan-Meier analyses showed that EFT had a significant effect on the achievement of MM5mg (p<0.0001, log-rank test; HR 1.82, p<0.0001). Notably, EFT was efficacious for any type of MG, and the inclusion of IVMP resulted in earlier and more frequent achievement of MM5mg (p=0.0352, log-rank test; HR 1.46, p=0.0380). In addition, early administration of calcineurin inhibitors also promoted MM5mg achievement. CONCLUSION: Early cycles of intervention with EFT and early use of calcineurin inhibitors provides long-term benefits in terms of achieving therapeutic targets for generalised MG, regardless of clinical subtype.

Proteolytic ectodomain shedding of muscle-specific tyrosine kinase in myasthenia gravis.

Autoantibodies to muscle-specific tyrosine kinase (MuSK) proteins at the neuromuscular junction (NMJ) cause refractory generalized myasthenia gravis (MG) with dyspnea more frequently than other MG subtypes. However, the mechanisms via which MuSK, a membrane protein locally expressed on the NMJ of skeletal muscle, is supplied to the immune system as an autoantigen remains unknown. Here, we identified MuSK in both mouse and human serum, with the amount of MuSK dramatically increasing in mice with motor nerve denervation and in MG model mice. Peptide analysis by liquid chromatography-tandem-mass spectrometry (LC-MS/MS) confirmed the presence of MuSK in both human and mouse serum. Furthermore, some patients with MG have significantly higher amounts of MuSK in serum than healthy controls. Our results indicated that the secretion of MuSK proteins from muscles into the bloodstream was induced by ectodomain shedding triggered by neuromuscular junction failure. The results may explain why MuSK-MG is refractory to treatments and causes rapid muscle atrophy in some patients due to the denervation associated with Ab-induced disruption of neuromuscular transmission at the NMJ. Such discoveries pave the way for new MG treatments, and MuSK may be used as a biomarker for other neuromuscular diseases in preclinical studies, clinical diagnostics, therapeutics, and drug discovery.

Association of immune-mediated necrotizing myopathy with HLA polymorphisms.

Immune-mediated necrotizing myopathy (IMNM) is a type of autoimmune myositis typically characterized clinically by proximal muscle weakness with elevated creatine kinase levels, pathologically by myofiber necrosis and regeneration with paucity of lymphocytic cell infiltration, and serologically by the presence of either of two myositis-specific autoantibodies, anti-SRP, and anti-HMGCR antibodies. However, the HLA loci and alleles associated with IMNM are still not fully understood at least partly because IMNM was a relatively recently established condition. In this study, we genotyped the six HLA loci (HLA-A, -B, -C, -DRB1, -DQB1 and -DPB1) in 250 patients (237 patients over age 18 years and 13 juvenile patients) diagnosed with IMNM based on clinicopathological features and autoantibody information and performed a case control study with Japanese healthy subjects. In the adult patients, specific HLA alleles associated with IMNM were identified at all HLA loci, with DRB1*08:03 showing the strongest association (OR = 2.5; p = 0.00000017). Furthermore, subgroup analysis with various clinical information showed that C*03:04 (OR = 3.7; p = 0.00012) was a higher risk allele for collagen disease in adult patients, and B*13:01 (OR = 23.2; p = 0.021) and C*03:04 (OR = 5.8; p = 0.0074) were higher risk for juvenile patients with anti-HMGCR antibody-positive IMNM. These findings will help to better understand the HLA genetic background and features of IMNM in designing future studies.