Abstract: Objective To know more about polymyositis (PM/DM) complicated by interstitical lung disease (ILD).Methods Clinical analysis of 14 patients with PM/DM complicated by inters titial lung disease (ILD).Results Male to female ration was 8∶6,averge age is 43.7,and average duration of misdiagnosis was 6.2 months,there were 22 patients misdiagnosed for respiratory system diseases and 21 patients for inflammation diseases.Conclusion Misdiagnoses are unusual between age and sex.The syndromes of ILD,which occur before those of PM/DM easily.limitations of acknowledge of PM/DM,the low specificity and sensitivity of examination.Biopsy through video-assistant thorascope (VATS) can increase the diagnoses of PM/DM with ILD.

Key words: PM/DM, LID, Misdiagnosis