[Hypersensitivity pneumonitis caused by Lyophyllum aggregatum in two sisters]

We encountered two sisters with hypersensitivity pneumonitis caused by Lyophyllum aggregatum. In Case 1, the patient was a 47-year-old woman who consulted Iiyama Red Cross Hospital because of a non-productive cough. She had worked with Lyophyllum aggregatum cultures for 7 years. In 1996, she complained of a dry cough, and had had a severe cough in November 1998. She was admitted to Iiyama Red Cross Hospital because of dyspnea on effort. Laboratory data revealed a high level of C-reactive protein. Chest radiography and CT scanning showed ground glass opacities in both lower lobes, and centrilobular nodules. Bronchoalveolar lavage fluid revealed a decrease in the CD4/CD8 ratio, and the lymphocyte fraction was very high. Transbronchial lung biopsy revealed lymphocytic granuloma and interstitial thickening, and the lymphocyte stimulation test was positive for Lyophyllum aggregatum. Case 2 occurred in the 51-year-old sister of Patient 1. She had worked with Lyophyllum aggregatum cultures for 10 years. In 1994, she had experienced dyspnea and a dry cough while working. In January 1999, she was admitted to Iiyama Red Cross Hospital because of a dry cough, sputum and chest oppression. Chest radiography and CT scanning revealed ground glass opacities in both lower lobes and centrilobular nodules. The CD4/CD8 ratio in the bronchoalveolar lavage fluid was low, and the lymphocyte fraction conspicuously high. The transbronchial lung biopsy revealed lymphocytic granuloma and interstitial thickening. The lymphocyte stimulation test was negative for Lyophyllum aggregatum. She was discharged and returned to work, but the dry cough and low-grade fever recurred. However, the occupational provocation test is not regarded as positive because chest radiography, laboratory examinations, and a pulmonary function test were not performed. The symptoms of both cases were eliminated only on isolation of the antigen. There has not been any previous report of hypersensitivity pneumonitis caused by Lyophyllum aggregatum.