Background Some patients with idiopathic interstitial pneumonia (IIP) show autoimmune features. Interstitial pneumonia with autoimmune features (IPAF) was recently proposed as a research concept in these patients. However, retrospective studies reported conflicting results of its prognosis. Therefore, this study was conducted to prospectively evaluate the clinical significance of autoimmune features in patients with IIP.
Methods This nationwide multicentre study prospectively enrolled consecutive patients with IIP. At the diagnosis, we systematically evaluated 63 features suggestive of connective tissue diseases using a checklist including symptoms/signs and autoantibodies, which contained most items of the IPAF criteria and followed up with the patients. Clinical phenotypes were included in a cluster analysis.
Results In 376 patients with IIP enrolled, 70 patients (18.6%) met the IPAF criteria. The proportion of patients with IPAF was significantly lower in idiopathic pulmonary fibrosis (IPF) than in non-IPF (6.0% vs 24.3%, respectively). During a median observation period of 35 months, patients with IPAF more frequently developed systemic autoimmune diseases and had less frequent acute exacerbation of IIPs than patients with non-IPAF. IPAF diagnosis was significantly associated with better survival and was an independent positive prognostic factor in total and patients with non-IPF. Cluster analysis by similarity of clinical phenotypes identified a cluster in which there was a higher number of women, and patients had more autoimmune features and a better prognosis than other clusters.
Interpretation These observations suggest that some patients with IIP show autoimmune features with distinct characteristics and favourable prognosis. However, we were not able to determine the appropriate therapies for these patients.
- connective tissue disease associated lung disease
- idiopathic pulmonary fibrosis
- interstitial fibrosis
Data availability statement
All data relevant to the study are included in the article or uploaded as supplementary information.
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Contributors NE and TSu contributed to the study conception and design. NE, SH, NI, YK, TS, HT, YI, HI, YT, SIz, YY, YT, YN, MT, KY, SIm, NK, TSa, TA, HMu, MK, NH, HC, SA, SM, HU, HMa, YK, MK, KM, MM, HH, TF and YN contributed acquisition of data. NE, KM and NO analysed and interpreted the data. NE drafted the manuscript. SH, NI, YK, TS, HT, YI, HI, YT, SI, YY, YT, YN, MT, KY, SI, NK, ST, TA, HM, MK, NH, HC, SA, SM, HU, HM, YK, MK, KM, MM, HH, TF, YN, NO and TS contributed to critical revision for important intellectual content. NE, SH, NI, YK, TS, HT, YI, HI, YT, SI, YY, YT, YN, MT, KY, SI, NK, TSa, TA, HM, MK, NH, HC, SA, SM, HU, HM, YK, MK, KM, MM, HH, TF, YN, NO and TSu approved the final version of manuscript to be published.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Competing interests YK has received personal fees from Asahi Kasei Pharma Corp., from Boehringer Ingelheim Co., Ltd., from Janssen Pharmaceutical K.K., from Eisai Inc., from Kyorin Pharmaceutical Co., Ltd., from Mitsubishi Tanabe Pharma, from Novartis Pharma K.K., and from Shionogi & Co., outside the submitted work. YI has received grants from Japanese ministry of Health, Labour, and Welfare, grants from Japan Agency for Medical Research and Development, and lecture fee from Boehringer Ingelheim and Shionogi outside the submitted work. YN has received grants and personal fees from Nippon Boehringer Ingelheim Co., Ltd., grants and personal fees from MSD K.K., grants and personal fees from Ono Pharmaceutical Co., Ltd., grants and personal fees from Taiho Pharmaceutical Co., Ltd., grants and personal fees from Chugai Pharmaceutical Co., Ltd., grants and personal fees from Asahi Kaesi Pharma Corporation, grants and personal fees from Eli Lilly Japan K.K., and grants from Bonac Corporation, outside the submitted work. HM has received grants and personal fees from Daiichi Sankyo, grants and personal fees from MSD, grants and personal fees from Sumitomo Dainippon Pharma, grants and personal fees from Taisho Toyama Pharmaceutical, grants and personal fees from Astellas Pharma, grants and personal fees from Boehringer Ingelheim, grants and personal fees from Shionogi, grants from Taiho Pharmaceutical, grants from Ono Pharmaceutical, grants from Takeda Pharmaceutical, grants from Eli Lilly Japan, grants from Novartis Pharma, grants from Fujifilm Pharma, grants from Meiji Seika Pharma, grants from Toyama Chemical, grants from Eisai, grants from Chugai Pharmaceutical, personal fees from Pfizer, personal fees from Kyorin Pharmaceutical, and personal fees from AstraZeneca, outside the submitted work. TS has received lecture fees from Boehringer Ingelheim and Shionogi, outside the submitted work.
Provenance and peer review Not commissioned; externally peer reviewed.