A 73-year-old woman presented with cough and exertional dyspnea in summer. Chest computed tomography (CT) showed diffuse centrilobular nodules with ground-glass opacities compatible with non-fibrotic hypersensitivity pneumonitis (HP). After admission, her symptoms and radiological findings improved without any treatment. Summer-type HP was suspected because of the presence of the serum-specific Trichosporon asahii antibodies; however, her symptoms recurred in winter. To identify causative antigens, we conducted an environmental investigation at her home, and yellow stains were detected on the bathtub.
According to the environmental investigation report, the provocation test was performed twice, including and excluding the bathroom. Her symptoms recurred only when she used the bathroom. Therefore, we confirmed the bathroom to be the causative environment of the disease. Her symptoms did not recur after the bathroom was renovated. Effective antigen avoidance was achieved with minimal home modifications.
In summary, we experienced a case of recurrence of HP that tested positive for anti-T. asahii antibodies in winter. Environmental investigation and environmental provocation tests were effective in determining the causative environment of the HP.