TLR9 and dermatomyositis: Studies have shown that TLR9 exerts its role in liver injury, systemic lupus erythematosus and lung cancer through regulating microRNA expression levels.21, 22, 23 miR‐7 is an immune‐related microRNA that is decreased in serum samples of DM patients.24 Besides, TLR9 suppressed miR‐7 expression level to promote PIK3R3/Akt pathway, thus to enhance the growth and metastasis of lung cancer cells.25 Therefore, we speculated that NETs‐TLR9‐miR‐7 might involve in the differentiation of MFs in the progression of PF.