Idiopathic interstitial pneumonia (IIP), or noninfectious pneumoniaare a class of diffuse lung diseases. Is a term used for a type of diffuse parenchymal lung disease (DPLD), also called interstitial lung disease (ILD).
There are seven distinct subtypes of IIP.

Histologic classification

Classification can be complex, and the combined efforts of clinicians, radiologists, and pathologists can help in the generation of a more specific diagnosis.

Idiopathic

Idiopathic

Idiopathic is an adjective used primarily in medicine meaning arising spontaneously or from an obscure or unknown cause. From Greek ἴδιος, idios + πάθος, pathos , it means approximately "a disease of its own kind". It is technically a term from nosology, the classification of disease...

 interstitial pneumonia can be subclassified based on histologic appearance into the following patterns:

Histology	Clinical Correlates
Desquamative interstitial pneumonia Desquamative interstitial pneumonia Desquamative interstitial pneumonia is a form of idiopathic interstitial pneumonia featuring elevated levels of macrophages.Its name is derived from the former belief that these macrophages were pneumocytes that had desquamated....  (DIP)	DIP
Diffuse alveolar damage Diffuse alveolar damage Diffuse alveolar damage is a histological pattern in lung disease. It is seen in acute respiratory distress syndrome , transfusion related acute lung injury and acute interstitial pneumonia .-Prevalence:...  (DAD)	ARDS, AIP, TRALI Transfusion related acute lung injury In medicine, transfusion related acute lung injury is a serious blood transfusion complication characterized by the acute onset of non-cardiogenic pulmonary edema following transfusion of blood products....
Nonspecific interstitial pneumonia Nonspecific interstitial pneumonia Non-specific interstitial pneumonia is a form of idiopathic interstitial pneumonia.It has a better prognosis than usual interstitial pneumonia....  (NSIP)	NSIP
Respiratory bronchiolitis Respiratory bronchiolitis Respiratory bronchiolitis interstitial lung disease refers to a form of idiopathic interstitial pneumonia associated with smoking.It is a histological finding, not a pathological description...	RB-ILD
Usual interstitial pneumonia Usual interstitial pneumonia Usual interstitial pneumonia is a form of lung disease characterized by progressive scarring of both lungs. The scarring involves the supporting framework of the lung. UIP is thus classified as a form of interstitial lung disease. The term "usual" refers to the fact that UIP is the most common...  (UIP)	CVD, IPF Idiopathic pulmonary fibrosis Idiopathic pulmonary fibrosis is a chronic, progressive form of lung disease characterized by fibrosis of the supporting framework of the lungs... , drug toxicity, pneumoconiosis Pneumoconiosis Pneumoconiosis is an occupational lung disease and a restrictive lung disease caused by the inhalation of dust, often in mines.-Types:Depending upon the type of dust, the disease is given different names:...
Organizing pneumonia	Cryptogenic organizing pneumonia
Lymphoid interstitial pneumonia (LIP)	LIP

Usual interstitial pneumonia is the most common type.

Development

Table 1: Development of the (histologic) idiopathic interstitial pneumonia classification
UIP=usual interstitial pneumonia; DAD=diffuse alveolar damage; NSIP=non-specific interstitial pneumonia; DIP=desquamative interstitial pneumonia; RB=respiratory bronchiolitis; BIP=bronchiolitis obliterans interstitial pneumonia; OP=organizing pneumonia; LIP=lymphoid interstitial pneumonia; LPD=lymphoproliferative disease (not considered a diffuse lung disease); GIP=giant cell interstitial pneumonia; HMF=heavy metal fibrosis, no longer grouped with diffuse lung disease

Lymphoid interstitial pneumonia was originally included in this category, then excluded, then included again.