[The clinical significance of myositis-specific antibodies in polymyositis/dermatomyositis associated interstitial lung diseases].

Objective: To investigate the profile and clinical significance of myositis-specific antibody spectrum (MSAs) in patients with polymyositis/dermatomyositis-associated interstitial lung disease (PM/DM-ILD). Methods: Sera from 74 patients with PM/DM-ILD, 29 patients with SLE and 32 healthy controls were collected and Euroline Autoimmune Inflammatory Myopathies 16 Ag kit was used for detecting MSAs . The clinical data of all patients were collected from medical records. Statistical analysis was performed using One-way ANOVA, t -test, rank sum test, χ(2) test or Fisher's exact test. Results: The overall detection rate of MSAs in 74 patients with PM/DM-ILD was 86.5%, significantly higher than that in patients with SLE and healthy controls (χ(2)=66.24, 69.85, P <0.01). According to the diagnostic criteria of PM/DM, 18 of 74 patients were definitely diagnosed, 11 were preliminarily diagnosed and 45 were suspected, in which the detection rate of MSA was 83.3%, 90.9% and 86.7%, respectively .The detection rates of MSAs in 17 PM-ILD and 57 DM-ILD were 82.4% and 87.7% respectively. The anti-ARS and anti-MDA5 were the two most common subtypes of MSAs in patients with PM/DM-ILD, the positive rates being 59.5% and 25.7%, respectively . The incidence of CADM, acute/subacute ILD and 90-day mortality in the anti-MDA5 positive group (χ(2)=12.945, 23.203, 26.434, P <0.05) was significantly higher than those of the anti-ARS group and the MSA-negative group, while the incidence of helitrope rash, V-rash, fever was significantly higher than the anti-ARS positive group (χ(2)=11.462, 5.895, 10.609, P <0.05). The incidence of muscle weakness in anti-Jo-1 group was significantly higher than that in the non-Jo-1 antibody group (χ(2)=3.991, P <0.05), while other clinical features were not statistically significant between the anti-Jo-1 and the non-Jo-1 anti-ARS positive groups ( P >0.05). Conclusion: The detection rate and accuracy of MSAs in polymyositis/dermatomyositis with ILD was very high, which was useful for early diagnosis of the disease, and severity and prognosis assessment. It is strongly recommended that MSAs should be detected in patients with clinical suspicion of PM/DM-associated interstitial lung diseases.