摘要目的:讨论骨骼肌特异性酪氨酸激酶抗体（MuSK-Ab）滴度与重症肌无力（MG）疾病严重程度和预后的关联。方法:采用前瞻性队列研究的方法，对2018年5月至2020年6月期间在中国医学科学院北京协和医院神经科诊断的骨骼肌特异性酪氨酸激酶抗体阳性重症肌无力（MuSK-MG）病例进行临床研究。共入组33例MuSK-MG，按照入组时是否曾接受免疫治疗分组，按照美国重症肌无力协会（MGFA）分型对初治（未经过任何免疫性治疗）患者进一步分组。28例患者接受了随访，随访结束时按照MGFA工作组的干预后状态（PIS）进行分组。25例患者接受了免疫治疗，按照治疗方式分为单用激素组（17例）和激素联合免疫抑制剂（IS）组（8例）。检验MGFA各组、PIS各组之间的抗体差异用Kruskal-Wallis法，检验治疗前后和不同治疗方式之间的抗体差异用Mann-Whitney U法。 结果:入组的MuSK-MG中男11例，女22例，发病年龄48（18，73）岁，初治16例，经治（已用过至少1次糖皮质激素或IS治疗）17例，在初治患者中不同MGFA分型的抗体浓度差异有统计学意义（ P=0.04），初治者在随访结束时 MuSK-Ab滴度显著低于入组时（中位数0.87比1.20， P=0.01）。24例（85.7%）达到了良好预后（PIS-PR/MM），1例（3.6%）达到改善（PIS-I），3例（10.7%）病情加重（PIS-W），各组之间MuSK-Ab滴度差异无统计学意义（ P=0.21），不同治疗组之间MuSK-Ab滴度差异无统计学意义（ P=0.95）。 结论:在初治患者当中，MuSK-Ab水平与疾病严重程度相符，免疫治疗可使抗体滴度下降。抗体的变化与激素用量相关，与预后分级不符。

abstractsObjective:To determine the correlation between the titer of anti-muscle-specific tyrosine kinase (anti-MuSK) antibodies (Abs) and the severity and prognosis of Musk-associated myasthenia gravis (Musk-MG).Methods:A total of 33 MuSK-MG patients diagnosed at Department of Neurology, Peking Union Medical College Hospital from May 2018 to June 2020 were prospectively included. Patients were divided into different groups according to immune state, and the immune naive patients were further divided by the Myasthenia Gravis Foundation of America (MGFA) classification. There were 28 Musk-MG patients who completed the follow-up and subdivided into different groups according to post-intervention status (PIS). Twenty-five patients who received immunotherapy were divided into corticosteroid monotherapy group ( n=17) and corticosteroid combined with immunosuppressant group ( n=8). The comparison of Ab titers between different MGFA groups and PIS groups was determined by Kruskal-Wallis method, and the comparison of Ab titers between different time points was analyzed by Mann-Whitney U method. Results:There were 11 males and 22 females included in the study, with an onset age of 48 (18, 73) years, of which 16 cases were immune naive and 17 cases were treated with corticosteroids or immunosuppressant at least once. In immune naive population, a significant difference of Ab titers among different MGFA phenotypes was detected ( P=0.04). Ab titers were reduced by immunosuppression therapy (the median value decreased from 1.20 to 0.87, P=0.01). Twenty-four (85.7%) MuSK-MG patients achieved a good prognosis (PIS-PR/MM), 1 (3.6%) case achieved improvement (PIS-I), and 3 (10.7%) patients′ condition worsened (PIS-W), there was no significant difference of Ab titers among the three groups ( P=0.21). Meanwhile, there was no significant difference of Ab titers between different treatment groups ( P=0.95). Conclusions:In the immune naive state, the concentration of MuSK-Ab is consistent with the severity of the disease, and the Ab titers decrease after immunotherapy. Change of Ab titers is related to the daily dosage of corticosteroid and is not consistent with PIS grades.