Introduction: The classification of the idiopathic interstitial pneumonias includes seven clinico-pathologic entities. The diagnosis is based on a multidisciplinary approach, integrating the clinical evaluation, the high-resolution computerised tomography, and the pathological pattern.
State of the art: A definitive diagnosis of idiopathic pulmonary fibrosis relies on the association of a suggestive clinico-radiological profile and a pathological pattern of usual interstitial pneumonia. Nonspecific interstitial pneumonia is a recently described clinico-pathologic entity, with a better prognosis than that of idiopathic pulmonary fibrosis. Cryptogenic organising pneumonia has been included in the group of idiopathic interstitial pneumonias because of its idiopathic and multifocal characteristics, although it does not predominate in the lung interstitium. Desquamative interstitial pneumonia and respiratory bronchiolitis with interstitial lung disease are rare entities with predominance in young smoking adults. Lymphoid interstitial pneumonia, usually encountered in the context of Sjögren's syndrome, is very rare in its idiopathic form. Acute interstitial pneumonia is responsible for idiopathic acute respiratory distress syndrome.
Perspectives: The current classification of idiopathic interstitial pneumonias better defines the diagnostic criterias of each clinico-pathologic entity, and is expected to facilitate clinical research.
Conclusions: This classification has clinical implications, with prognostic and therapeutic significance.