Unusual systemic disorders associated with interstitial lung disease.

Interstitial lung disease often starts as a reaction to a causative insult or antigen, such as an inhaled environmental organic or inorganic dust and autoimmune mediated injury. When no underlying cause can be found, the inflammatory change in the gas exchanging parts of the lungs and associated fibrosis is called idiopathic pulmonary fibrosis (cryptogenic fibrosing alveolitis). The common causes of pulmonary fibrosis can be classified as granulomatosus, nongranulomatous, neoplastic, and iatrogenic. There are other multisystem disorders not included in this classification that are associated with interstitial lung disease. Amyloidosis, Behcet disease, Kikuchi disease, and Whipple disease are such multiorgan disorders that involve the lungs.