A Case of Hypersensitivity Pneumonitis Caused by Methotrexate

Background: Methotrexate (MTX) has been used to treat a wide range of malignant and benign diseases including osteosarcoma, advanced stage non-Hodgkin's lymphoma, psoriasis, severe rheumatoid arthritis, sarcoidosis, and Wegener's granulomatosis. MTX-induced lung injury occurs in up to 10% of treated patients. Although both acute and chronic presentations have been described, typical manifestation of MTX-induced lung injury is subacute with symptoms usually developing within several months after starting therapy. Nonspecific interstitial pneumonia (NSIP) is the most common histopathologic manifestation of MTX-induced lung disease, while bronchiolitis obliterans organizing pneumonia (BOOP) and diffuse alveolar damage (DAD) are less common. Granuloma formation is reported in 34.7%. In Korea, Two reports of MTX pneumonitis have been published. The one presented with NSIP and the other with DAD. We recently experienced a case of MTX pneumonitis with presentation of hypersensitivity pneumonitis.