Objectives:Lyophyllum aggregatum (LA)
is called Shimeji in Japanese and is eaten commonly as a
mushroom. Shimeji mushrooms are cultivated in an indoor
environment all year round. This study aimed to clarify the clinical
features of hypersensitivity pneumonitis (HP) induced by LA.
Patients and setting: Ten patients showed mild respiratory
symptoms including dry cough, sputum, and low-grade fever. We tried to
characterize the clinical features and the findings using chest
high-resolution CT (HRCT), pulmonary function tests (PFTs), and BAL
fluid (BALF) tests in patients with HP induced by LA. HP was diagnosed
from clinical features, HRCT findings, BALF findings, lung histology,
and lymphocyte stimulation tests (LSTs) for LA.
Results: Laboratory findings showed mean (± SD) elevated
levels of C-reactive protein (0.78 ± 1.3 mg/dL), erythrocyte
sedimentation rate (48 ± 23 mm/h), and γ-globulin
(26.9 ± 7.6%). PFTs revealed a slight decrease in the percentage
diffusing capacity of the lung for carbon monoxide, possibly due to the
presence of epithelial granulomas in the alveoli. Although 4 of 10
patients showed normal findings on the chest radiograph (CXR), chest
HRCT findings of all patients showed centrilobular small nodules and
diffuse ground-glass opacities. The BALF testing revealed an increase
in total cell counts, showing predominantly activated T lymphocytes.
The CD4/CD8 cell ratio was significantly decreased (0.5 ± 0.3). The
results of the LSTs were positive in seven of seven cases.
Conclusions: Since patients with HP induced by LA typically
have mild respiratory symptoms and sometimes normal CXR findings, their
conditions might remain undiagnosed. However, the chest HRCT images
showed the typical subacute phase of