[Methotrexate-induced interstitial pneumonitis in a child with acute lymphoblastic leukemia].

: We report a case of 5-year-old boy with acute lymphoblastic leukemia who developed interstitial pneumonitis induced by methotrexate (MTX). The patient was hospitalized with fever, cough, dyspnea and hypoxemia during maintenance treatment with low dose MTX and 6-mercaptopurine. A diagnosis of MTX pneumonitis was made based on the clinical findings, viral and serologic studies, negative microbiology and the radiological features. The patient recovered after cessation of the MTX treatment. Interstitial pneumonitis caused by MTX is well-recognized and the prevalence has been estimated to be 0.3-7.5% among patients with adult rheumatoid arthritis. However, there are few reports in the literature regarding this adverse effect in patients with leukemia. Furthermore, very few cases of childhood leukemia have been reported regarding MTX induced interstitial pneumonitis. Physicians should be aware of this rare complication during maintenance treatment with weekly low dose MTX for acute lymphoblastic leukemia in children.