Plasma proteomic profiling reveals KRT19 could be a potential biomarker in patients with anti-MDA5+ dermatomyositis

Objective To investigate the immune response–related protein profiling in plasma of patients with idiopathic inflammatory myopathies (IIMs), especially in anti-MDA5+ dermatomyositis (DM). Methods A total of 166 IIM patients and 107 healthy controls (HCs) were enrolled in our study. Ninety-two plasma immune response–related proteins were detected by Olink proteomics in 36 IIM patients and 25 HCs. The expression of plasma KRT19 was validated in another 130 IIM patients, 82 HCs, and 55 other rheumatic diseases. Results A total of 46 differentially expressed proteins were detected, including 12 upregulated proteins and 34 downregulated proteins in IIM patients compared with HCs. Pathway analysis revealed lactoferrin danger signal response pathway, TLR4 signaling and tolerance, infection, and IL-10 signaling pathway were activated. The immune response–related protein profiling significantly altered in anti-MDA5+ DM patients, with LAMP3, HSD11B1, and KRT19 significantly increased, while SH2D1A, ITGA11, TRIM21, CD28, ITGB6, and HEXIM1 tremendously decreased. In addition, KRT19 was significantly increased in IIM patients, especially in anti-MDA5+ DM patients with the diagnostic value of a significant area under the ROC curve of 0.881. Conclusion Immune response–related proteins are significantly altered in patients with anti-MDA5+ DM patients. KRT19 could be a potential biomarker for anti-MDA5+ DM patients. Key Points • What is already known on this topic? Anti-MDA5+ DM is a distinctive subtype of IIM. Plasma immune response–related proteins panel needs to be investigated. • What this study adds? Plasma protein profiling of immune response–related proteins significantly altered in patients with idiopathic inflammatory myopathies (IIM), especially in anti-MDA5+ DM patients. • How this study might affect research, practice, or policy? KRT19 could be a potential biomarker in patients with anti-MDA5+ dermatomyositis.