[A CASE OF FIBROTIC HYPERSENSITIVITY PNEUMONITIS IN WHICH A DRUG-INDUCED LYMPHOCYTE STIMULATION TEST FOR ISOCYANATE...

A 30-year-old man who had worked in the painting industry for the past year was referred to our hospital after developing progressive exertional dyspnea. A chest computed tomography scan showed a diffuse, random pattern of ground-glass opacities in the lungs. Bronchoalveolar lavage fluid (BALF) was predominantly lymphocytic (49.2%), and bronchoscopic cryobiopsy showed fibrotic interstitial proliferation around the small bronchi and Masson's bodies. The drug-induced lymphocyte stimulation test (DLST) for isocyanate (hexamethylene diisocyanate [HDI]) reagent was positive in blood and the BALF samples. The patient was diagnosed with hypersensitivity pneumonitis, and isocyanates (HDI) were suspected as the allergen based on the effectiveness of antigen avoidance, occupational history, DLST results, and a multidisciplinary discussion. Avoiding the antigen with a leave of absence and changing jobs, along with corticosteroids and mycophenolate mofetil treatment resulted in partial improvement of both the reticular shadows in the lungs and respiratory function. In recent years, isocyanate-induced hypersensitivity pneumonitis has become rare, probably because of improvements in working environments, but healthcare providers must still be aware of it as an occupational allergy. Although DLST alone cannot definitively diagnose hypersensitivity pneumonia, when combined with other findings it may serve as a useful adjunct diagnostic tool, as in this case.