Isolated Chronic Cough with Sputum Eosinophilia Caused by Humicola fuscoatra Antigen: The Importance of Environmental Survey for Fungus as an Etiologic Agent

We report here a 35-year-old man with isolated chronic cough associated with sputum eosinophilia in which Humicola fuscoatra (H. fuscoatra) antigen was an etiologic agent. He was admitted for the diagnosis and the treatment of his severe nonproductive cough. Although 80% of the nucleated cells in his induced sputum were eosinophils, he did not have bronchial hyperresponsiveness to methacholine or heightened bronchomotor tone. Bronchodilator therapy was not effective against his coughing. His cough worsened on his return home, suggesting the existence of some etiologic agent in his house. H. fuscoatra was isolated from his house, and the bronchoprovocation test with H. fuscoatra antigen was positive: i.e., development of coughing and decrease in capsaicin cough threshold (capsaicin concentration causing five or more coughs) from the prechallenge value of 31.3 µM to 1.95 µM at 6 and 48 hr, respectively, after the challenge. In addition, repeated environmental survey for fungi was suggestive of the importanc...