[Humidifier lung].

Breathing air from a humidifier or an air conditioning unit contaminated by various microorganisms can cause an acute lung disease involving fever, cough and dyspnea, termed "humidifier fever". This type of hypersensitivity pneumonitis was first described in 1959 by PESTALOZZI in the Swiss literature and subsequently by BANASZAK et al. in the Anglo-American. Here a chronic form of this disease which led to pulmonary fibrosis is described: A 37-year-old woman who works in a cheese shop presented with dyspnea which had been progressive over two years, weight loss, a diffuse reticular pattern radiographically and a severe restrictive defect in lung function tests. Open lung biopsy revealed chronic interstitial and alveolar inflammation with non-caseating granulomas and fibrotic changes. Circulating immune complexes and precipitins against the contaminated humidifier water and cheese mites were found, but no antibodies suggesting legionnaires' disease. Two out of five otherwise healthy employees of this cheese shop, where a new humidifying system had been installed 7 years earlier, also had precipitins against the contaminated water from the humidifier and the cheese mites. Despite ending of exposure and longterm steroid and immunosuppressive therapy, the signs and symptoms of pulmonary fibrosis persisted. Contrary to the acute disease, this chronic form is termed "humidifier lung". The importance is stressed of investigating the possibility of exposure to contaminated humidifiers or air conditioning units in all cases of newly detected pulmonary fibrosis.