[A case of rheumatoid arthritis complicated with methotrexate-induced pneumonitis and pneumocystis pneumonia].

: A 62-year-old woman with rheumatoid arthritis was given 4 mg/body methotrexate (MTX) every week and 5 mg prednisolone every day. She developed a severe cough starting in the evening after starting taking MTX and after a fever of 38 degrees and dyspnea appeared the patient was hospitalized. On admission, chest CT findings showed diffuse ground glass attenuation. Pathological findings of specimens obtained by transbronchial lung biopsy showed alveolitis with epithelioid cell granuloma. As a section of the specimen did not show cyst staining by Grocott stain, MTX-induced pneumonitis was diagnosed. The same day, methylprednisolone pulse therapy was started and trimethoprim-sulfamethoxazole (TMP-SMX) was given simultaneously, while MTX was discontinued. On hospital day 3, subsequent data showed a high serum level of beta-D glucan and a positive PCR result for Pneumocystis jiroveci in bronchoalveolar lavage fluid (BALF). Additional section of the specimen showed eosinophilic foamy areas on HE staining and cysts measuring 8 microm, consistent with the Pneumocystis jiroveci lesions by Grocott stain. We present a case of rheumatoid arthritis complicated by methotrexate-induced pneumonitis in which pneumocystis pneumonia was demonstrated by clinical and pathological findings.