Several recent reports have proposed that interstitial pneumonia centered around small airways may be a form of idiopathic interstitial pneumonia not included in previous classifications such as the American Thoracic Society/European Respiratory Society Consensus Classification. This concept is currently controversial, because some experts believe that these histologic findings are not a unique entity but are the sequelae of other established diseases.

Airway-centered interstitial fibrosis (ACIF) was recently described as an uncommon form of interstitial lung disease that clinically presents with progressive dyspnea and chronic cough. Most patients are middle-aged adults and there is a 2:1 female predominance. Although the lung fibrosis is predominantly airway centered, the condition generally behaves as an interstitial lung disease. Pulmonary function tests usually show restrictive lung changes. Chest radiography shows peribronchovascular fibrosis and interstitial thickening. Prognosis for these patients is variable, but most patients have a poor prognosis. ACIF is similar, but not identical, to another proposed uncommon disease, idiopathic bronchiolocentric interstitial pneumonia. Future studies will be necessary to determine whether ACIF is a specific entity or not and whether it is a form of idiopathic interstitial pneumonia or a common histopathologic response to a wide variety of lung insults.