Diffuse parenchyma lung disease (DPLD) encompasses a hetero-geneous group of disorders, characterized by a spectrum of inflammatory and fibrotic changes affecting alveolar walls and air spaces. They comprise over 200 entities and include a wide spectrum of diseases, many uncommon and many of unknown etiology. The incidence and prevalence rates of DPLD have not been precisely estimated due to difficulties in ascertaining a specific diagnosis on a specific disease.