放射免疫法定量检测乙酰胆碱受体抗体与重症肌无力患者临床特征的相关性

目的探讨乙酰胆碱受体抗体(AChR-Ab)与重症肌无力(MG)临床特征的相关性。方法采用放射免疫法检测115例MG患者及92例对照组(非MG神经系统疾病患者42例,健康体检者50名)血清AChRAb浓度,应用临床绝对评分记录MG患者病情严重程度。分析各组血清AChR-Ab浓度的差异,以及AChR-Ab浓度与MG患者临床特征的相关性。采用ROC工作特征曲线探讨AChR-Ab诊断MG的敏感度和特异度。结果MG患者血清AChR-Ab浓度中位数(四分位数间距,下同)为3.45(39.38)nmol/L,较非MG神经系统疾病患者[0(0)nmol/L]和健康体检者[0(0)nmol/L]增高(P0.01)。全身型MG(GMG)患者AChR-Ab浓度[25.45(46.14)nmol/L]较眼肌型MG(OMG)患者[0.58(3.56)nmol/L]增高(P0.01)。用ROC曲线法分析显示,以血清AChR-Ab浓度≥0.50nmol/L作为诊断MG界值时灵敏度为72.17%,特异度为100%,曲线下面积(AUC)=0.895(95%CI:0.849~0.941)。AChR-Ab浓度与发病年龄、病程及改良Osserman分型呈正相关(r=0.220,P0.05;r=0.184,P0.05;r=0.382,P0.01),但相关性较弱(均r0.5),与临床绝对记分无相关性(r=0.147,P0.05)。结论用放射免疫法检测血清AChR-Ab浓度诊断MG的灵敏度和特异度均高,有助于减少MG的漏诊率及误诊率,值得临床推广。     

Complement activation profiles in anti-acetylcholine receptor positive myasthenia gravis

Background and purpose

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.

Methods

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.

Results

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.

Conclusions

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.     

MuSK antibody-positive, seronegative myasthenia gravis in Korea.

Several reports from Western countries suggest differences in the clinical features of patients with muscle specific kinase (MuSK) antibody-positive and -negative seronegative myasthenia gravis (MG). We performed the first survey in Korea of MuSK antibodies, studying 23 patients with acetylcholine receptor (AChR)-antibody seronegative MG. MuSK antibodies were present in 4 (26.7%) of 15 generalized seronegative MG patients and none of 8 ocular seronegative MG patients. All four MuSK positive patients were females, with pharyngeal and respiratory muscle weakness, and required immunosuppressive treatment. However, overall disease severity and age at onset was similar to that of MuSK-negative MG and treatment responses were equally good.     

肌肉特异性受体酪氨酸激酶抗体阳性重症肌无力

目的 探讨不同血清抗体重症肌无力(MG)的临床特征.方法 用荧光免疫沉淀法(FIPA)和荧光免疫细胞染色法(CBA)检测119例MG患者血清乙酰胆碱受体抗体(AChR-Ab)和肌肉特异性受体酪氨酸激酶抗体(MuSK-Ab)水平.比较AChR-Ab阳性、MuSK-Ab阳性、血清抗体阴性MG的临床特征.结果 纳入119例患者中,90例AChR-Ab阳性(75.6%),29例阴性:其中5例MuSK-Ab阳性(17.2%),24例血清抗体阴性(82.8%).AChR-Ab阳性、MuSK-Ab阳性和血清抗体阴性MG 3组比较,男女比例和平均发病年龄差异均无统计学意义.3例MuSK-Ab阳性的患者主要表现为延髓肌受累;79.2%(19/24)的血清抗体阴性MG患者表现为美国MG协会(MGFA)Ⅰ型;2例MuSK-Ab阳性的患者MGFA≥Ⅲ型;MuSK-Ab滴度水平与患者病情严重程度相关(r=0.941,P=0.014);MuSK-Ab阳性的患者均未发现有胸腺的异常.结论 MuSK-Ab仅出现在AChR-Ab阴性患者的血清中.MuSK-Ab阳性的患者主要表现为延髓肌受累,病情较重且不伴有胸腺的病变.MuSK-Ab阳性的MG可能是不同于血清AChR-Ab阳性的MG的又一亚型.     

MuSK-positive myasthenia gravis is rare in the Polish population

Background and purpose:  MuSK-positive myasthenia gravis (MG) is diagnosed in 0–48% of cases with generalized seronegative MG in different populations. The presence of anti-MuSK antibodies generally relates to a severe course and lack of response to thymectomy. We analyzed for the first time the serology and clinical characteristics of MuSK-positive MG in the Polish population.
Methods:  One hundred and fifty-one patients were tested for the presence of anti-AChR and anti-MuSK antibodies: 62 with seronegative MG, including 14 with ocular seronegative MG, 48 age-matched patients with seropositive MG and 41 controls.
Results: All patients with seropositive MG and the disease controls were MuSK-negative. Anti-MuSK antibodies were detected only in four patients with seronegative MG (8.7% of generalized seronegative cases): three women and one man. All four had predominantly bulbar involvement, and underwent thymectomy, with no apparent benefit. All of them improved clinically after immunosuppressive treatment with remissions lasting up to 7 years.
Conclusion: MuSK-positive MG is rare in Polish population accounting for only 8.7% of seronegative cases with generalized MG. This is consistent with emerging evidence for lower MuSK antibodies at more northerly latitudes.     

Neurophysiological and mitochondrial abnormalities in MuSK antibody seropositive myasthenia gravis compared to other immunological subtypes.

OBJECTIVE: To compare the electrophysiological and histopathological features of immunological myasthenia gravis (MG) subtypes. METHODS: Fifty MG patients underwent clinical examination, MuSK-Ab and AChR-Ab analysis. The majority underwent quantitative and single-fiber electromyography (QEMG, SFEMG), repetitive nerve stimulation and deltoid muscle biopsy. From muscle specimens with histological mitochondrial dysfunction, we amplified mitochondrial DNA (mtDNA). In specimens with mtDNA deletions, the nuclear gene POLG1 was sequenced. RESULTS: Five AChR-Ab seropositive [AChR(+)] and 5 seronegative [AChR(-)] patients were MuSK-Ab seropositive [MuSK(+)]. Five of 7 neurophysiologically examined MuSK(+) patients (71%) had proximal myopathic pattern, compared to 7 of 31 MuSK(-)/AChR(+) patients (23%) (P=0.012). SFEMG was abnormal in all examined MuSK(+) patients. All 7 biopsied MuSK(+) and 32 MuSK(-) patients (89%) had cytochrome c oxidase (COX) negative fibers. Three of five MuSK(+) and 13 of 20 MuSK(-) patients analyzed had multiple mtDNA deletions but no POLG1 mutations. CONCLUSIONS: Similar degree of SFEMG abnormalities was present in proximal muscles among MuSK(+) and AChR(+) patients. Proximal myopathy was over-represented in MuSK(+) patients; however, both MuSK(+) and MuSK(-) patients had mild myopathy with frequent mitochondrial abnormalities. SIGNIFICANCE: The weakness in MuSK(+) patients is most likely due to disturbed neuromuscular transmission. The frequently encountered mitochondrial dysfunction in MG warrants further study.     

MG患者外周血Th17细胞与AChR抗体产生的关系研究

目的探讨重症肌无力(MG)患者外周血中Th17细胞及相关细胞因子白细胞介素17(IL-17)在MG发病中的作用。方法收集40例MG患者和10名健康人(对照组)外周血标本,采用流式细胞术检测外周血单个核细胞(PBMCs)中Th17细胞比例,反转录酶-聚合酶链锁反应(RT-PCR)检测PBMCs中维甲酸受体相关孤儿受体γt(RORγt)mRNA水平,ELISA检测血清中IL-17水平,放射免疫沉淀法检测血清中抗乙酰胆碱受体抗体(AChR-Ab)滴度;分离PBMCs中CD4~+T细胞和CD19~+B细胞与金黄色葡萄球菌肠毒素B(SEB)进行共培养,培养系统中加入人IL-17和(或)IL-21中和抗体,放射免疫测定法检测培养液中AChR-Ab滴度。采用MG评分(quantitative MG scoring system,QMGs)对MG的严重程度进行评估,并对MG患者的Th17细胞比例、RORγt mRNA和IL-17水平与病情QMGs的相关性,以及MG患者抗AChR-Ab滴度与PBMCs中Th17细胞比例的相关性进行分析。结果 MG患者PBMCs中Th17细胞比例[1.11%(0.90%,1.34%)]高于健康对照组Th17细胞比例[0.26%(0.08%,0.36%)](z=5.494,P0.001),且与疾病严重程度呈正相关(r=0.4394,P=0.0046);血清中IL-17水平和PBMCs中RORγt mRNA相对表达[分别71.46(53.91,104.76)pg/mL、2.63(1.94,3.12)]均较健康对照组[分别18.82(12.73,29.80)pg/mL、1.13(0.98,1.28)]显著增高(均P0.001);MG患者血清中抗AChR-Ab滴度[2.34(1.19,3.60)nmol/L]较健康对照组[-0.08(-0.24,-0.03)nmol/L]显著增高(z=4.662,P0.001),且与Th17细胞比例呈正相关(r=0.7066,P=0.0001)。MG患者外周血T、B细胞与SEB共培养后抗AChR-Ab水平高于未加入SEB时及健康对照(均P0.01);加入抗人IL-21或IL-17中和抗体后,两者AChR-Ab滴度与未加入抗体时AChR-Ab滴度比较均降低(均P0.05),且均仍高于MG患者未加入SEB时及健康对照(P0.01);在培养上清中同时加入抗人IL-21和IL-17中和抗体时AChR-Ab滴度明显低于加入单种抗体时,而与未加入SEB时及健康对照差异无统计学意义(均P0.05)。结论 MG患者外周血中Th17细胞可能通过IL-17促进AChR-Ab产生,参与疾病的病理过程。     

Chronic limb-girdle myasthenia gravis.

The existence of chronic "limb-girdle" form of myasthenia gravis (MG) has been questioned. We report here 12 such patients (10 women and two men) who constituted 3.8% of 314 MG patients in our study. The duration of disease ranged from 4 months to 7 years before the diagnosis. In almost all cases, the initial diagnosis was other than MG. None of the patients had any oculobulbar weakness. Acetylcholine receptor antibody was positive in five cases, although not all in the first assay. Repetitive nerve stimulation test was positive in all cases, although not necessarily the first time. Single-fiber EMG was positive in 11 cases. All patients responded to acetylcholinesterase inhibitors, and two thirds underwent immunotherapy. Diagnosis of limb-girdle MG requires a strong index of suspicion.     

Clinical and experimental features of MuSK antibody positive MG in Japan

We investigated the presence of antibodies (Abs) against muscle-specific tyrosine kinase (MuSK) in Japanese myasthenia gravis (MG) patients. MuSK Abs were found in 23 (27%) of 85 generalized seronegative MG (SNMG) patients but not in any of the ocular MG patients. MuSK Ab-positive patients were characterized as having female dominance (M:F, 5:18), age range at onset 18 to 72 (median 45) years old, and prominent oculobulbar symptoms (100%) with neck (57%) or respiratory (35%) muscle weakness. Limb muscle weakness was comparatively less severe (52%), thymoma absent. Most patients had good responses to simple plasma exchange and steroid therapy. MuSK IgG from all 18 patients was exclusively the IgG 4 subclass and bound mainly with the MuSK Ig 1–2 domain. Serial studies of 12 individuals showed a close correlation between the variation in MuSK Ab titers and MG clinical severity ( P  = 0.01 by Kruskal–Wallis). MuSK Ab titers were sharply decreased in patients who had a good response to early steroid therapy or simple plasma exchange, but there was no change, or a rapid increase on exacerbation after thymectomy. Measurement of MuSK Ab titers aids in the diagnosis of MG and the monitoring of clinical courses after treatment.     

Seronegative generalised myasthenia gravis: clinical features,antibodies, and their targets

Myasthenia gravis (MG) is a well-recognised disorder of neuromuscular transmission that can be diagnosed by the presence of antibodies to the acetylcholine receptor (AChR). However, some patients (about 15%) with generalised MG do not have detectable AChR antibodies. There is some evidence, however, that this "seronegative" MG is an antibody-mediated disorder. Plasma from patients with the disorder seems to contain various distinct humoral factors: IgG antibodies that reversibly inhibit AChR function; a non-IgG (possibly IgM) factor that indirectly inhibits AChR function; and an IgG antibody against the muscle-specific kinase (MuSK). The presence of antibodies against MuSK appears to define a subgroup of patients with seronegative MG who have predominantly localised, in many cases bulbar, muscle weaknesses (face, tongue, pharynx, etc) and reduced response to conventional immunosuppressive treatments. Moreover, muscle wasting may be present, which prevents complete response to these therapies.     

Single-fiber electromyography of masseter muscle in myasthenia gravis

Jitter after axonal microstimulation in the masseter muscle was studied in 30 consecutive patients (12 women) with myasthenia gravis (MG). Patients' mean age was 42.3 (12-75), median disease duration was 3 months (1-72), and onset was ocular (15 cases), oculobulbar (7), bulbar (6), or generalized (2). There were 23 newly-diagnosed patients. Nine cases developed purely ocular MG and 21 cases developed generalized MG. In the latter group, five subjects had a rapidly progressive course and 16 subjects had stable or well-controlled disease (MGFA grade 2-3). Six patients did not have circulating anti-acetylcholine receptor antibodies. Masseter single-fiber electromyography (SFEMG) was abnormal in 6 of 9 ocular MG patients and in all generalized cases (overall sensitivity 27 of 30 cases or 90%; confidence interval 79.3%-100.0% at P = 0.95). Masseter should be considered for SFEMG in diagnosis of MG, especially in cases with bulbar onset.     

High-dose cyclophosphamide in refractory myasthenia gravis with MuSK antibodies

We describe a 48-year-old woman with seronegative myasthenia gravis (MG) and high-titer of anti-MuSK antibody. She had severe bulbar and respiratory weakness with minimal limb weakness for 2 years. Her disease responded poorly to all the conventional immunosuppressive regimens. Treatment with immunoablative dose of cyclophosphamide led to dramatic and sustained remission of her symptoms. High-dose cyclophosphamide is an effective alternative in patients with unusually refractory disease.     

Clinical aspects of MuSK antibody positive seronegative MG

Serum antibodies to muscle-specific receptor tyrosine kinase were detected in 12 of 32 patients with generalized seronegative MG. All were women, with onset between ages 21 and 59 years. Seven had prominent neck, shoulder, or respiratory muscle weakness and little or delayed ocular muscle involvement. The response to cholinesterase inhibitors was variable, and electromyographic findings suggested myopathy in several. None improved after thymectomy. All patients improved after plasma exchange, and most had a good response to selected immunotherapy. MuSK antibody status should help diagnose MG with atypical presentations and ensure appropriate patient treatment.     

Gabapentin may be hazardous in myasthenia gravis

A patient with painful neuropathy developed ocular, facial, and masticatory weakness and fatigue after 3 months of gabapentin (GBP) treatment (400 mg/day). An elevated level of serum acetylcholine receptor antibodies (AChR-Ab) was detected. The patient recovered following pyridostigmine therapy and withdrawal of GBP and, 2 years later, is practically asymptomatic despite positive AChR-Ab. Because of this clinical observation, we gave 150 mg/kg GBP to rats with experimental autoimmune myasthenia gravis (EAMG). Repetitive nerve stimulation at 3-Hz was performed, and the 5th/1st amplitude ratio was used to calculate the decremental response. In all EAMG rats, GBP induced a transient, abnormal decrement (7-20%) 90 to 240 min after administration. No decrement was induced by GBP in normal rats. Thus, GBP aggravates the decrement in EAMG. The mechanism involved in the hitherto unreported possible unmasking of myasthenia gravis (MG) by GBP is unknown. Gabapentin should be used with caution in this disease.     

糖皮质激素冲击治疗后重症肌无力早期一过性加重的机制研究

目的 探讨糖皮质激素冲击(GI)治疗后重症肌无力(MG)早期一过性加重的机制.方法 选取2012年1月～2013年6月诊治的125例MG患者,并给予GI治疗,统计分析并进行治疗前后临床评分和血清抗胆碱受体抗体滴度(AchR-Ab)、免疫球蛋白IgG和补体C3水平、肌电图检测.结果 GI治疗MG后,7天有效率为57.78％,28天有效率为75.56％,其中肌无力一过性加重发生率为36.0％;肌无力加重后患者临床绝对评分明显高于加重前,差异具有统计学意义(P＜0.05);桡神经和腋神经低频重复电刺激波幅递减程度明显高于加重前,差异具有统计学意义(P＜0.05);加重前后患者血清AchR-Ab、IgG和C3水平差异均无统计学意义(P＞0.05).结论 GI治疗MG后,具有早期一过性加重发生的风险,这可能与激素抑制神经递质的传递有关,但与体内抗体、补体水平变化无关.     

Seronegative myasthenia gravis: disease severity and prognosis

Around 10-20% of myasthenia gravis (MG) patients do not have acetylcholine receptor (AChR) antibodies (seronegative), of whom some have antibodies to a membrane-linked muscle specific kinase (MuSK). To examine MG severity and long-term prognosis in seronegative MG compared with seropositive MG, and to look specifically at anti-AChR antibody negative and anti-MuSK antibody negative patients. Seventeen consecutive seronegative non-thymomatous MG patients and 34 age and sex matched contemporary seropositive non-thymomatous MG controls were included in a retrospective follow-up study for a total period of 40 years. Clinical criteria were assessed each year, and muscle antibodies were assayed. There was no difference in MG severity between seronegative and seropositive MG. However, when thymectomized patients were excluded from the study at the year of thymectomy, seropositive MG patients had more severe course than seronegative (P < 0.001). One seropositive patient died from MG related respiratory insufficiency. The need for thymectomy in seronegative MG was lower than in seropositive MG. None of the seronegative patients had MuSK antibodies. This study shows that the presence of AChR antibodies in MG patients correlates with a more severe MG. With proper treatment, especially early thymectomy for seropositive MG, the outcome and long-term prognosis is good in patients with and without AChR antibodies.     

Decremental response of the nasalis and hypothenar muscles in myasthenia gravis

Repetitive nerve stimulation (RNS) is a standard diagnostic procedure in myasthenia gravis (MG). Although RNS sensitivity is highest in weak muscles, RNS is easier to perform in distal muscles that are often not affected. Twenty-five patients with MG were assessed to compare the sensitivity of RNS of the nasalis muscle to that of the hypothenar muscles. Abnormal decrement was found in hypothenar muscles in 9 patients (36%) and in the nasalis muscle in 13 patients (52%). RNS of the nasalis muscle appeared more useful to detect abnormal neuromuscular transmission in patients with oculobulbar MG (5 of 5) than hypothenar RNS (1 of 5). In patients with generalized MG, hypothenar muscles had a similar yield of abnormal RNS tests.     

Two cases of thymoma-associated myasthenia gravis without antibodies to the acetylcholine receptor

Thymoma-associated myasthenia gravis is considered a more severe disease compared with non-thymomatous myasthenia gravis and is generally associated with antibodies to the acetylcholine receptor (AChR-Ab). Even though a single case of thymoma-associated myasthenia gravis with anti-muscle specific kinase (MuSK) antibodies has been reported, to our knowledge, seronegative thymoma-associated myasthenia gravis has not been described. We report on two cases of this disease without antibodies to AChR or MuSK as a further evidence of the variability of myasthenia gravis in terms of antibody profile and thymic pathological findings.     

重症肌无力合并多发性肌炎两例临床分析并文献复习

目的观察重症肌无力(MG)合并多发性肌炎(PM)的临床特征及疗效,并探讨其共病机制及治疗方法,提高临床识别度。方法报道作者医院收治的两例MG合并PM患者的临床资料,结合文献分析其发病特点、实验室检查、疗效及预后等。结果两例患者临床症状以四肢无力、球肌麻痹、肌肉疼痛为主要表现,疲劳现象不明显,实验室检查可见肌酶升高,偶有心肌受累,肌电图提示肌源性损害;单用溴吡斯的明治疗效果不佳,联合激素和免疫制剂治疗反应良好。结论 MG合并PM的病例少见;MG患者在规范化治疗过程中若出现肌肉疼痛、肌酶谱升高,或疲劳现象消失、眼肌症状不明显等表现时,需行肌电图、肌活检等明确有无合并肌肉疾病的可能;治疗上以免疫治疗为主,急重症者建议使用丙种球蛋白或血浆置换等方法。     

Monocyte-mediated immunosuppression in chronic multiple sclerosis: implications for therapy

The goal of immunotherapy in multiple sclerosis (MS) is to halt disease progression by correcting an immunologic abnormality. The experiments described here sought an abnormality of immunoregulation. Specifically, the immunosuppressive activity of adherent monocytes in an in vitro assay of immunoglobulin-secreting cells was tested. Although the peak response was slightly lower, the induction, development and shutdown of the response by MS cells reproduced that of control cells. Most importantly, adherent monocytes from patients with MS exerted the same maximal suppression as did monocytes from controls. Further experiments are required to determine if the adherent monocyte is an appropriate target for immunotherapy in MS.