[A case of farmer's lung disease manifested by smoking cessation].

A 40-year-old man, a cattle hoof-chipper, was admitted to Hokkaido University Hospital in June 2002 for a workup of the occasional fever, cough and dyspnea that had affected him at work since March 2002. He had not smoked since January 2001. On admission, he had a marked increase in the proportion of lymphocytes (62.9%) and the CD 4/CD 8 ratio (3.0) in the bronchoalveolar lavage fluid. Serum precipitating antibody against Thermoactinomyces vulgaris was detected. The results of a transbronchial lung biopsy were unremarkable. Since his chest radiographs at the previous clinic showed small nodular opacities, we diagnosed farmer's lung on the basis of the diagnostic criteria defined by the Research Group of the Ministry of Health, Labor and Welfare. He was treated with prednisolone and advised to wear a protective mask, and his symptoms have not recurred since. This is an interesting case in which smoking cessation appears to have unmasked latent farmer's lung.