[The concept of interstitial pneumonia with autoimmune features (IPAF)]

Interstitial lung diseases (ILD) are a heterogeneous group of respiratory diseases often related to connective tissue diseases. Some patients will develop an ILD with autoimmune features without reaching the recommended criteria for autoimmune diseases. Their management is difficult because they have both features for idiopathic and connective tissue disease. To better identify these patients, the concept of interstitial pneumonia with autoimmune features (IPAF) has been created. The diagnosis relies on ILD without identified cause and the presence of at least one defined criterion among 2 of the 3 following domains: clinic, serologic, and morphologic. The mean age at diagnosis is 60, a sex ratio of 1/1, and depending on the authors close to 20% of patients with IPAF will develop a connective tissue disease according to the international criterion. Their prognosis is better than for patients with idiopathic ILD and with an average 5-year survival of 70%. Older age at diagnosis, a pattern of usual interstitial pneumonia, and an impaired diffusing capacity for carbon monoxide have been identified as poor prognosis factors. The treatment relies on usual care for chronic respiratory diseases and is often associated with immunosuppressive and/or antifibrotic therapies. The objective of this classification is to better characterize these patients and improve their management.