NCIt definition : An inflammatory interstitial lung disease caused by hypersensitivity reaction to inhalation
or ingestion of antigens. The antigens are usually related to the patient's occupation.
It can present as an acute illness with flu-like symptoms, subacute with repeated
episodes of pneumonia, or chronic with dyspnea and productive cough. The majority
of patients recover following the cessation of the exposure to the antigen that causes
the disease. Chronic exposure may eventually progress to interstitial lung fibrosis.;