Some patients with idiopathic interstitial pneumonias (IIPs) have clinical features that suggest autoimmune process but not fulfill established criteria for connective tissue disease (CTD). Different terms and criteria have been proposed to describe these patients, which includes undifferentiated connective tissue disease (UCTD), lung dominant connective tissue disease (LD-CTD), and autoimmune-featured interstitial lung disease (AIF-ILD). To marshal these ununiform classification criteria, the "European Respiratory Society/American Thoracic Society Task Force on Undifferentiated Forms of Connective Tissue Disease-associated Interstitial Lung Disease" proposed a consensus regarding the nomenclature and classification criteria for patients with IIP and features of autoimmunity with the term "interstitial pneumonia with autoimmune features" (IPAF). It was reported that patients with IPAF accounted for 7.3%∼34.1% of patients with interstitial lung disease (ILD). Survival, rate of progressing to CTD, appropriate treatment, and treatment response are not yet elucidated. Furthermore, it is not determined whether IPAF is a distinct category of ILD or simply a part of IIP. These questions should be elucidated by future prospective cohort studies. Hopefully, rheumatologists should participate in not only clinical trials but also in multidisciplinary discussions for IPAF.
Keywords: autoimmune feature; connective tissue disease; idiopathic interstitial pneumonia; interstitial lung disease.