目的：观察特发性炎性肌病（idiopathic inflammatory myopathy, IIM）合并间质性肺病（interstitial lung di- sease, ILD）患者血清中抗黑素瘤分化相关基因5（melanoma differentiation associated gene 5, MDA5）抗体的表达水平，探讨抗MDA5 抗体与IIM合并ILD（IIM-ILD）临床特征、严重程度及6个月死亡率之间的关系，为寻找新的免疫干预新途径积累实验数据。方法：采用酶联免疫吸附试验检测104例IIM不合并ILD患者19例和IIM-ILD患者85例[其中多发性肌炎（polymyositis, PM）4例，皮肌炎（dermatomyositis, DM）8例，无肌病性皮肌炎（amyopathic dermatomyositis, ADM）7例, PM-ILD 17例, DM-ILD 25例, ADM-ILD 43例]，以及13名正常对照者血清中的抗MDA5抗体水平，分析该抗体与患者肺功能[包括用力肺活量（forced vital capacity, FVC%）]与一口气呼吸法一氧化碳扩散功能（single breath, carbon monoxide diffusing capacity, DLCO/SB）、肺结构包括高分辨率CT评分及半年生存率间的关系。结果：ADM-ILD患者血清中的抗MDA5抗体水平较正常对照组、IIM不合并ILD组及PM-ILD组明显增高（P<0.005）;相比DM-ILD患者，ADM-ILD患者血清中的抗MDA5抗体水平增高（P<0.05）;该抗体水平与IIM患者肺功能间无相关性（FVC%，r=-0.044 25，P=0.757 9;DLCO/SB，r=-0.068 39，P=0.633 5），而与肺结构改变呈显著正相关（r=0.387 9，P=0.000 2）;抗MDA5阳性DM患者的半年内的生存率与抗MDA5阴性患者相比明显降低（77.55%比100.00%），差异有统计学意义（P=0.000 2）。结论：采用酶联免疫吸附试验测得的血清抗MDA5抗体水平，与DM尤其是ADM合并ILD患者的肺功能、肺结构破坏严重程度及半年生存率密切相关。

Objective: To study the expression level of anti-melanoma differentiation gene 5 antibody (anti-MDA5 antibody) in serum of idiopathic inflammatory myopathy (IIM) patients associated with interstitial lung disease (ILD), and to explore the relationship between anti-MDA5 antibody and clinical characteristics, severity and 6-month mortality of IIM-ILD patients for providing laboratory evidences to delineate new immune intervention pathway. Methods: The expression of anti-MDA5 antibody in serum of 104 patients with IIM or IIM-ILD, including polymyositis 4 cases, dermatomyositis 8 cases, amyopathic dermatomyositis, 7 cases, polymyositis-ILD 17 cases, dermatomyositis-ILD 25 cases, amyopathic dermatomyositis-ILD 43cases, and normal control group was detected by ELISA, and the relationships between anti-MDA5 antibody and lung function [FVC% and DLCO/SB (single breath, carbon monoxide diffusing capacity)], lung structure [HRCT score (high resolution CT score)] and 6-month survival were analyzed. Results: In patients with amyopathic dermatomyositis (ADM), the serum level of anti-MDA5 antibody was higher than that of normal controls, patients with dermatomyositis (DM), IIM not associated with ILD and polymyositis (PM) with ILD(P<0.005). Compared with DM-ILD patients, the serum level of anti-MDA5 antibody in patients with ADM-ILD was increased (P<0.05). There was no correlation between anti-MDA5 antibody level and lung function in patients with IIM (FVC% r=-0.04425 P=0.7579, DLCO/SB, r=-0.06839 P=0.6335), and was positively correlated with lung structural changes (r=0.3879 P=0.0002). The 6-month mortality of IIM patients with positive anti-MDA5 antibody was significantly different from that of anti-MDA5 antibody negative patients (P=0.0002). Conclusions: The anti-MDA5 antibody level detected by ELISA is closely correlated with lung function, severity of lung structural damage and mortality in patients with DM-ILD, especially ADM-ILD.