To investigate the clinical and immunological features of rapid progressive interstitial lung disease(ILD) in patients with idiopathic inflammatory myopathy(IIM).

The medical records of 146 adult IIM patients associated with ILD in Peking University People's Hospital from February 1996 to February 2015 were retrospectively analyzed. They were divided into three subgroups: the classic DM, PM and the clinical amyopathic dermatomyositis(CADM), and were further stratified based on with or without rapid progressive ILD(RP-ILD). Chi-squared test was used for group comparisons of categorical data and independent-sample t test for numerical data.

① Among 146 patients, 62(42.5%) developed RP-ILD. The prevalence of RP-ILD in CADM was signifcantly higher than dermatomyositis(DM) and polymyositis(PM). ② ILD occurred after or at the same time with IIM in more than 90% of patients. ILD arising before or simultaneously with DM(named "early-onset ILD") tended to progress rapidly. ③ For the DM group, mechanic's hands, fever, lymphopenia, hypoxemia, hypoalbuminemia, and the elevation of globulin α₁ were associated with RP-ILD. CADM-ILD with weakness of swallow muscles, increasing C-reactive protein(CRP) and globulin α₂, decreased vital capacity and the relatively high level of segmented granulocytes in bron-choalveolar lavage fluid tended to undergo a rapid progressive clinical course. Additionally, the decreased free triiodothyronine(FT3) and the elevation of tumor markers including carcino-embryonic antigen(CEA), neuron specific enolase(NSE), cytokerantin-19-fragment(CYFRA211) and ferritin were significantly more frequent both in DM and CADM with RP-ILD(P<0.05) patients. ④ According to multivariate analysis, mechanic's hands [HR=31.747, 95%CI(2.367, 425.817),P=0.009] and the elevation of CEA [HR=57.047, 95%CI(1.140, 2 854.885),P=0.043] and CRP [HR=31.568, 95%CI(1.818, 548.093),P=0.018] were potential predictive factors for RP-ILD in DM and CADM patients, respectively.

The prevalence of RP-ILD in CADM is higher than DM and PM. ILD usually occurs after or simultaneously with IIM, early-onset ILD in DM patients tends to progressive rapidly. Increased tumor markers and decreased FT3 indicate the deterioration of disease. Mechanic's hands and the elevation of CEA and CRP are potential predictive factors for RP-ILD in DM and CADM patients, respectively.

Myositis; Lung disease, interstitial; Allergy and Immunology