[Chronic type hypersensitivity pneumonitis].

The clinical features and chest X-ray appearances of chronic type hypersensitivity pneumonitis closely resemble those of idiopathic interstitial pneumonia. Therefore, it is very difficult to make a correct diagnosis without detailed information. Our study showed that bronchoalveolar lavage and lung biopsy are useful examinations for the differential diagnosis of these two diseases. The characteristic finding of bronchoalveolar lavage of chronic type hypersensitivity pneumonitis is still lymphocytosis, as is also seen in the acute type. The pathological findings of chronic type hypersensitivity pneumonitis are alveolitis with marked lymphocyte infiltrations and granuloma formation although the number of granulomas is low. Recently, we experienced five patients with chronic type farmer's lung. The average age of these five patients was significantly older than that of acute type farmer's lung. They had engaged in farming after the onset of their disease, which suggested continuous chronic exposure to mouldy hay. It is concluded that patients with hypersensitivity pneumonitis, especially aged people, should avoid antigen exposure and should be followed up the progress of the disease with intensive care.