INTRODUCTION: The term ?interstitial pneumonia with autoimmune features? (IPAF) was proposed by ERS/ATS in 2015 to unify study groups although it is still a heterogeneous group of patients. Based on studies, only a small percentage of patients with IPAF will develop connective tissue disease (CTD) in the future. So far, literature on the differences between the pathobiology of IPAF and connective tissue disease-associated interstitial lung disease (CTD-ILD) has been scarce. There are also no prospective studies on bronchoalveolar lavage (BAL) in IPAF.

OBJECTIVES: The purpose of the study is to assess whether there are significant differences in BAL in patients with IPAF and CTD-ILD.

METHODS: We conducted a prospective study in 2 groups of patients: with IPAF and CTD-ILD. All these patients were presented at multidisciplinary team meetings and assessed by a pulmonologist, a rheumatologist and a radiologist to avoid misdiagnosis. BAL was conducted according to standards.

RESULTS: 41 patients were included in the study: 20 with IPAF, 21 with CTD-ILD (10 sclerodermas, 3 antisynthetase syndromes, 3 rheumatoid arthritis, 1 myositis, 1 Sjogren?s syndrome, 3 overlap syndromes). In the IPAF group we noticed a lower total cell count (23.75±18.24 vs. 35.65±18.56; p=0.04522), a lower level of eosinophils (0.7 [0.3-1.3] vs.2,3 [0.7-5.3]; p=0.01683) and a higher level of macrophages (83 [71.75-88.17] vs. 66,7 [51-82]; p=0.03349) than in the CTD-ILD group.

CONCLUSIONS: The results may indicate less severe inflammation in the IPAF group vs. CTD-ILD.