To systematically review the latest research progress on the pathogenesis of pulmonary fibrosis associated with idiopathic inflammatory myopathies (IIM-PF), so as to provide theoretical basis for clinical diagnosis, treatment and prognosis evaluation of the disease.

A comprehensive search was conducted in databases such as PubMed, Embase, Web of Science and CNKI. The included literature was analyzed and summarized from the aspects of immune inflammation, genetic factors, epithelial-mesenchymal transition (EMT) and environmental factors.

The pathogenesis of idiopathic inflammatory myopathy-related pulmonary fibrosis involves many aspects. First, for immune inflammatory mechanism, abnormal activation of immune cells and excessive release of inflammatory cytokines play a key role in the occurrence and development of IIM-PF. CD4+ T cells, CD8+ T cells, B cells, macrophages and other immune cells are involved in the immune response process. For example, CD4+ T cells can differentiate into Th1, Th2, Th17 and other subsets, and secrete corresponding cytokines to regulate the inflammatory response. In addition, autoantibodies, such as anti-Jo-1 antibody, anti-Mi-2 antibody, etc., are closely related to the occurrence and progression of IIM-PF. These autoantibodies can directly damage lung tissue or induce immune complex deposition, leading to inflammatory reaction and fibrosis. Second, genetic susceptibility is an important risk factor for IIM-PF. Studies have found that multiple gene loci are associated with the occurrence of IIM-PF, such as HLA-DRB1, HLA-DQA1, PTPN22, etc. These genes may affect the function of immune cells, the regulation of inflammatory response and the process of EMT, thereby increasing the susceptibility to IIM-PF. In addition, epigenetic modifications, such as DNA methylation, histone acetylation and non-coding RNA regulation, also play an important role in the pathogenesis of IIM-PF. Besides, epithelial-mesenchymal transition (EMT) is a key process in the formation of pulmonary fibrosis. In IIM-PF, various factors, such as inflammatory cytokines, oxidative stress and mechanical stress, can induce alveolar epithelial cells to undergo EMT, transform into mesenchymal cells, and secrete a large amount of extracellular matrix, leading to the accumulation of extracellular matrix and the formation of pulmonary fibrosis. Further, environmental factors, such as smoking, dust exposure, viral infection, etc., may trigger or aggravate the occurrence and development of IIM-PF. Smoking can induce oxidative stress and inflammatory response in the lung, damage alveolar epithelial cells, and promote the occurrence of EMT. Dust exposure can cause chronic inflammation and fibrosis in the lung. Viral infection, such as influenza virus, respiratory syncytial virus, etc., can activate the immune system, induce the release of inflammatory cytokines, and participate in the pathogenesis of IIM-PF.

The pathogenesis of IIM-PF is complex, which is the result of the interaction of multiple factors such as immune inflammation, genetic factors, EMT and environmental factors. Although great progress has been made in the research on the pathogenesis of IIM-PF in recent years, the specific molecular mechanism is still not fully clear. In the future, more in-depth research is needed to further clarify the pathogenesis of IIM-PF, so as to provide new targets and strategies for clinical diagnosis and treatment.