Objective  To explore the expression and significance of myositis antibodies in patients with idiopathic inflammatory myopathy (IIM).

  Methods  The medical materials of 49 IIM hospitalized patients with myositis antibodies detection in Anqing Hospital Affiliated to Anhui Medical University from August 2018 to April 2021 were collected, and the correlations between myositis antibodies and clinical features, laboratory indexes and prognosis of IIM patients were analyzed.

  Results  Among 49 IIM patients, 37 cases were positive for myositis antibodies. The positive rates of anti ARS antibody (32.7%) and anti MDA5 antibody (30.6%) were the highest among the myositis specific autoantibodies (MSAs), and anti SSA/Ro antibody, a myositis associated antibody (MAA), also had a very high positive rate (49.0%), most of patients were combined with MSAs. Patients with positive anti-ARS antibodies were less likely to have heliotrope rash, V-shaped sign, shawl sign and Gottron sign, and were more likely to have mechanic's hand, myalgia and interstitial lung disease, and also had a high lymphocyte count than patients who were negative for anti-ARS (P < 0.05). Patients with anti-SSA/Ro-positive antibody were prone to occur interstitial lung disease and had a higher mortality (P < 0.05). Patients with positive anti-Mi-2 antibody had higher incidence rates of dysphagia and higher levels of aspartate transaminase (AST), creatine kinase (CK) and lactate dehydrogenase (LDH) than patients who were negative for anti-Mi-2 (P < 0.05). Patients with positive anti-transcription intermediary factor-1 γ(anti-TIF1γ) antibody were more likely to have tumors (P=0.0015). Anti-MDA5 antibody was more common in dermatomyositis (DM) and amyopathic dermatomyositis (ADM) patients. Compared with negative patients, positive patients were more likely to have fever, heliotrope rash, shawl sign, Gottron sign, arthralgia, interstitial lung disease, higher mortality, less myalgia and muscle weakness, lower levels of lymphocyte count, CK and LDH (P < 0.05). Logistic regression analysis identified anti-ARS-antibodies as a protective factor for V-shaped sign and Gottron sign (P < 0.05), aminoacyl-tRNA synthetase (Jo-1) antibody as an independent risk factor for the mechanic's hand (OR=15.417, 95%CI was 2.641 to 90.000, P=0.002), anti-Mi-2 antibody as independent risk factor for dysphagia (OR=21.000, 95%CI, 1.544 to 285.685, P=0.022), anti-TIF1γ antibody as an independent risk factor for tumors (OR=44.000, 95%CI, 2.709 to 714.585, P=0.008), anti-MDA5 antibody as an independent risk factor for fever, heliotrope rash, arthralgia, interstitial lung disease and a protective factor for myalgia, muscle weakness (P < 0.05). Cox regression analysis identified anti-MDA5 antibody as an independent risk factor for death in IIM patients (HR=16.023, 95%CI, 1.944 to 135.066, P=0.010).

  Conclusion  Myositis antibodies are highly positive in IIM patients, and their subtypes are closely related to clinical features, laboratory indexes and prognosis of patients. Detection of myositis antibodies has great significance in guiding the diagnosis, treatment and prognosis of IIM patients.