Phenotypic clusters and survival analyses in interstitial pneumonia with myositis-specific autoantibodies

Abstract Background Interstitial pneumonia (IP) is one of the common pulmonary complications of idiopathic inflammatory myopathy (IIM), among which myositis-specific autoantibodies (MSAs) are specific for diagnosing and predicting the prognosis of IIM. However, IP patients with MSAs (MSA-IP) have not been well described. The study aimed to explore the phenotypic clusters and prognosis of MSA-IP patients. Methods A total of 124 MSA-IP patients were prospectively enrolled for analysis. Serum MSAs were detected using immunoprecipitation. Radiographic patterns of IP were determined according to the classification of idiopathic IPs. Clusters of MSA-IP patients were identified using cluster analysis. Potential risk factors for acute-onset disease and short-term prognoses were also analysed. Results There were four clusters of MSA-IP patients. Cluster 1 patients were elderly with chronic onset and a usual interstitial pneumonia pattern on computed tomography. Cluster 2 patients were all positive for anti-aminoacyl-tRNA antibodies, were predominantly female and had frequent respiratory symptoms. Patients in cluster 3 showed multi-system involvement with a nonspecific interstitial pneumonia pattern. Patients in cluster 4 had severe respiratory symptoms with anti-MDA5 antibodies. The patients in cluster 3 (OR 6.682, 95% CI 1.560–28.622, P =0.011) and cluster 4 (OR 6.057, 95% CI 1.715–21.388, P =0.005) were susceptible to acute-onset disease. The patients in cluster 4 were prone to disease progression (HR 2.711, 95% CI 1.128–6.519, P =0.034), which was consistent with the Kaplan–Meier curves. Conclusions Four distinctive clusters were determined by cluster analysis, suggesting the characteristics, serological antibodies and prognosis of patients with MSA-IP.