[Chronic and acute hypersensitivity pneumonitis in a dairy farmer and his son].

We encountered a dairy farmer and his son with farmer's lung who had worked on the same farm for 25 years and 5 years, respectively. The son was admitted to our hospital because of cough, sputum, and shortness of breath. Chest computed tomography (CT) on admission revealed diffuse ground-glass opacities in both lung fields. Following admission, the clinical symptoms and radiological findings improved spontaneously without specific treatment. A provocation test (following return to work on the farm) elicited recurrence of the symptoms and radiological findings. He was diagnosed with acute hypersensitivity pneumonitis (HP) based on the clinical findings. After quitting his job, no reccurence was noted. The farther was admitted to our hospital complaining of repeated episodes of cough and high fever. He had been diagnosed with lung fibrosis 10 years previously. Chest CT on admission revealed progression of thin-walled cystic changes over ten years. Following admission, his symptoms improved without medication. However, because he has continued working on the farm, his radiological findings have gradually deteriorated. He was diagnosed with chronic HP based on his clinical features. These cases are suggestive of farmer's lung with familial occurrence, difference between acute HP and chronic HP, and long-term prognosis.