Chronic hypersensitivity pneumonitis induced by Shitake mushroom spores associated with lung cancer

A 61-year-old man was admitted to our hospital with a 6-month history of productive cough. He, along with his wife, had been involved with Shiitake mushroom cultures for a period of 12 years. On admission, chest radiography showed bilateral fine-nodular shadow and CT scans showed reticulonodular opacities and a ground-glass appearance predominantly in the subpleural area in both lungs, and a mass in the left S-6. Resected pathological specimens obtained by left lower lobectomy revealed lung adenosquamous carcinoma (stage IB), interstitial changes accompanied with lymphocyte proliferation and fibrosis, and granuloma with giant cells. Serum precipitins for Shiitake mushroom antigens were positive. The productive cough improved after the hospital admission and occurred again when he returned to work with the Shiitake mushroom production. Therefore, chronic hypersensitivity pneumonitis (HP) caused by Shiitake mushroom spores was diagnosed. Moreover, his wife was found to have HP caused by mushrooms at this time. There are only two previous reports of chronic HP caused by Shiitake mushroom in Japan, and this is the first case of chronic HP associated with lung cancer.