Hypersensitivity pneumonitis due to Bunashimeji mushrooms in the mushroom industry

Background: Detection of hypersensitivity pneumonitis (HP) in employees involved in the Bunashimeji mushroom industry is difficult. The level of precipitating antibody is not related with the prediction of progression and resolution of HP. The aims of this study were to examine the actual prevalence of HP in the Bunashimeji industry and the clinical differences among selected employees.

Methods: One hundred and fourteen employees worked in Bunashimeji enterprises. These subjects were divided into the following subgroups: office workers, pickers/packers with mask and pickers/packers without mask. We measured serum Krebs von der Lungen-6 (KL-6), surfactant protein (SP)-A and SP-D, and examined the stimulation index (SI) due to Bunashimeji spores. Chest high-resolution computed tomography (HRCT), pulmonary function tests and bronchoalveolar lavage (BAL) were performed for select employees who showed positive SI values (>200%) to examine the clinical differences.

Results: The proportion of respiratory symptoms was significantly higher in the pickers/packers than that in the office workers. The picker/packer group had high serum KL-6 concentrations and SI compared with the office worker group. Thirty select employees were divided into the following three subgroups: HP, select employees without HP, and SI <400% and KL-6 <500 U/ml , using high SI levels (>400%) and positive serum KL-6 concentration (>500 U/ml). Four exhibited ground glass opacities with centrilobular fine nodules on HRCT, and 8 had high numbers of lymphocytes in the BAL fluid. The BAL findings and serum KL-6 concentrations showed significant differences among the three groups.

Conclusions: Four employees were evaluated as having HP. Serum KL-6 and SP-D may be related to the resolution of HP in addition to SI and chest HRCT.