Background: Flammulina velutipes is called the Enoki mushroom in Japanese and is cultivated indoors. Mushroom workers face occupational exposure to a tremendous number of fungi and organic antigens capable of causing hypersensitivity pneumonitis (HP). One worker employed at an Enoki farm developed HP due to Penicillium citrinum. This study investigated new cases of HP among the workers cultivating Enoki.
Methods: Serum Krebs von der Lungen-6 (KL-6), surfactant protein (SP)-A and SP-D were measured. Lymphocyte stimulation tests (LST) and double immunodiffusion tests (DIT) were performed to identify P. citrinum. Workers showing high levels of KL-6, SP-A, or SP-D and a high LST value or positive DIT were identified and then were further examined by chest computed tomography, bronchoalveolar lavage and transbronchial lung biopsy. The initial patient and new HP patients were defined as the HP group and the other participants were defined as the non-HP group.
Results: Forty-eight Enoki workers participated in the study. Four of nine workers who met the criteria for further examinations were diagnosed as having HP due to P. citrinum. In comparison between non-HP group and HP group, KL-6, SP-D and LST values were significantly higher in HP group. There was a strong correlation between KL-6 and SP-D. DIT had high sensitivity and high specificity.
Conclusions: KL-6, SP-D, LST, and DIT were useful for detecting HP patients. KL-6 was the most useful predictor of HP in this study. DIT was useful not only as a predictor of HP but also as a detector of the causative antigen.