Because this was a retrospective study, complete clinical data were not available for every patient. high-resolution CT or lung biopsy. The majority of patients (95%) with mild and moderate groups on basis of pulmonary function tests. Compared to the anti-PM/Scl-100 group, the occurrence of clinical characteristics was not significantly different from Vancomycin hydrochloride the anti-PM/Scl-75 group, except the levels of C-reactive protein and erythrocyte sedimentation rate in the anti-PM/Scl-75 antibody-positive group were higher (< 0.05). All patients with positive Ro-52 antibodies had ILD and were more likely to develop skin rash in the group with Ro-52 (= 0.024). With a follow-up of the present cohort, 70.8% improved with treatment, but 16.7% of patients are easy to relapse. Conclusion The anti-PM/Scl antibody occurred frequently in DM/PM patients, ILD was the major clinical feature, especially in patients combined with Ro-52. Some patients may complicate with ILD alone without Tmem33 extrapulmonary manifestations. Anti-PM/Scl antibodies positive patients were responsive to treatment. Keywords: anti-PM/Scl antibodies, interstitial lung disease, dermatomyositis, polymyositis, systemic sclerosis Introduction A characteristic feature of patients with connective tissue diseases (CTDs) is the presence of autoantibodies in their sera that target intracellular components. Autoantibodies often characterize patients with distinct clinical features and often have different prognoses. Anti-PM/Scl antibodies were first described in patients with overlap syndrome of polymyositis (PM) and scleroderma (Scl) or systemic sclerosis (SSc) (1, 2). Anti-PM/Scl antibodies are a heterogeneous group of autoantibodies directed to several proteins of the nucleolar PM/Scl macromolecular complex. The two main autoantigenic protein components were identified and termed PM/Scl-75 and PM/Scl-100 based on their apparent molecular weights (3, 4). Anti-PM/Scl antibodies have great diversity in their prevalence and clinical characteristic among different races and countries. A study showed that the anti-PM/Scl was found in 31% of PM/SSc patients, 11% of dermatomyositis (DM) patients, 8% of patients with PM alone, and 2% of SSc patients (5). De Lorenzo et al. reported muscle weakness, mechanic’s hands, Raynaud syndrome, and interstitial lung disease (ILD) occurred frequently in anti-PM/Scl-positive patients (6). However, few reports have described cases with anti-PM/Scl antibodies in China. The clinical features, and differences between anti-PM/Scl-75 and PM/Scl-100, were previously unknown. To address these questions, we initially identified Chinese patients with the anti-PM/Scl antibody, reviewed all of their clinical data including response to treatment with follow-up, then compared the differences between patients with anti-PM/Scl-75 and PM/Scl-100. Methods and Materials Patients Anti-PM/Scl antibodies were screened from the immune laboratory, with a total of about 5,000 samples between May 2015 and Oct 2020, and about 300 serum samples were from the ILD service. The following data of patients with anti-PM/Scl antibodies were obtained from the medical records: age, gender, pulmonary function tests (PFTs), electrocardiogram, ultrasonic cardiogram, pulmonary high-resolution CT (HRCT), levels of creatine kinase (CK) and lactate dehydrogenase (LDH), C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), ferritin, immunoglobulin, presence of myositis-associated antibodies, and other myositis-specific autoantibodies (MSAs). If anti-PM/Scl-positive patients were combined with other MSAs, they were excluded. Response to treatment was documented, including complete follow-up on all patients. Pulmonary function test (PFT) abnormalities manifested by restrictive changes [forced vital capacity (FVC) < 80% and diffusing capacity of carbon monoxide (DLCO) < 70% predicted]. The diagnosis of ILD depended on HRCT and/or lung biopsy. The ILD patterns were classified as usual interstitial pneumonia (UIP), organizing pneumonia (OP), non-specific interstitial pneumonia (NSIP), and lymphocytic interstitial pneumonia (LIP). Patients with ILD were divided into three groups according to the initial PFT values in reference to the previous studies: the mild group (% predicted FVC > 75% and % predicted DLCO > 55%), the moderate group (% predicted FVC from 75 to 50% or %predicted DLCO from 55% to > 35%), and the severe group (% predicted FVC < 50% and % predicted DLCO < 35%) (7, 8). According to Vancomycin hydrochloride the consensus statement of the American Thoracic Society on idiopathic pulmonary fibrosis, Vancomycin hydrochloride a decrease or increase of 10% in FVC was.