Desquamative Interstitial Pneumonia Complicated with IgG4-related Lung Disease.

As an idiopathic interstitial pneumonia, desquamative interstitial pneumonia (DIP) is an uncommon form of interstitial lung disease and is considered to be a smoking- or dust inhalation-related interstitial pneumonia in the majority of cases. However, the details regarding immunoglobulin G4 (IgG4)-related lung disease remain unclear and controversial. We herein report the first case of DIP complicated with IgG4-related lung disease. Even if a patient has a smoking history, we emphasize the importance of exploring the association between DIP and IgG4-related lung disease to clarify the pathogenesis of these two disorders.