<prompt> Most common cause of idiopathic interstitial pneumonia is-SarcoidosisOrganizing pneumoniaIdiopathic pulmonary fibrosisLipoid pneumonia  <response>: Ans. is c i.e., Idiopathic pulmonary fibrosis Diffuse parenchymal lung disease DPLD of known cause eg, drugs or association eg, rheumatic diseaseIdiopathic interstitial pneumonia lIPsGranulomatous DPLD eg, sarcoidosisOther forms of DPLD eg, LAM, PLCH, etc Non-familial80 percentFamilial2 to 20 percent ChronicfibrosingAcutesubacutefibrosingSmokingrelatedo Idiopatic pulmonary fibrosiso Idiopathic nonspecific interstitial pneumoniao Cryptogenic organizing pneumoniao Acute interstitial pneumoniao Respiratory bronchiolitis interstitial lung diseaseo Desquamative interstitial pneumonia o Diffuse parenchymal lung diseases consist of disorders of known causes rheumatic disease, environmental or drug related as well as disorders of unknown cause.o The latter include idiopathic interstitial pneumonias, granulomatous lung disorders eg, sarcoidosis, and other forms of interstitial lung disease including lymphangioleiomyomatosis, pulmonary Langerhans cell histiocytosis histiocytosis X, and eosinophilic pneumonia.o The interstitial pneumonias are further categorized as chronic fibrosing, acute or subacute fibrosing, or smoking related.o Lymphocytic interstitial pneumonia is typically associated with other disease processes, such as rheumatic disease or immunosuppression; idiopathic lymphocytic pneumonia is rare.o DPLD: diffuse parenchymal lung disease; IIP: idiopathic interstitial pneumonia; LAM: lymphangioleiomyomatosis; PLCH: pulmonary Langerhans cell histiocytosishistiocytosis X. 