Louis Hamman and Arnold Rich published a paper describing diffuse interstitial fibrosis of the lung in 1944. They described thickening of the alveolar interstitium and an area of dense fibrotic scar tissue within the lung. Liebow and Carrington heralded the modern era of interstitial lung disease histo-pathology with the notion that IIP could be split into separate pathological subtypes in 1969. In 2002, a panel of experts sponsored jointly by the American Thoracic Society (ATS) and the European Respiratory Society (ERS) released an official statement for the purpose of providing a new and comprehensive classification of IIP that considered all clinical, radiographic and pathological features.
Interstitial lung disease (ILD):Interstitial lung disease (ILD), sometimes called diffused parenchymal diseases is a group of diseases characterized by a combination of chronic inflammation within the lung, consisting of an accumulation of chronic inflammatory cells (predominantly lymphocytes and macrophages) and increased levels of numerous pro-inflammatory cytokines, chemokines, and cell surface molecules; and varying degrees of lung fibrosis.
American Thoracic Society/European Respiratory Society (ATS/ERS) 2002 consensus classification statement:Histopathologic classification separating the IIPs into seven clinicopathologic entities (in order of relative frequency)
- Idiopathic pulmonary fibrosis (IPF) (47-64%)
- Nonspecific interstitial pneumonia (NSIP) (14-36%)
- Respiratory bronchiolitis ILD(10-17%)
- Cryptogenic organizing pneumonia (4-12%)
- Acute interstitial pneumonia (AIP) (< 2%)
- Lymphoid interstitial pneumonia (LIP) (< 2%)