[Pneumonitis associated to methotrexate].

Methotrexate (MTX) is a folic acid antagonist that inhibits cellular reproduction. MTX has been shown to be an effective anti-inflammatory agent. Acute interstitial pneumonitis is the main pulmonary side effect during MTX treatment. We report a case of MTX pneumonitis in a 56-year old woman with autoimmune thrombocytopenia who presented with subacute nonproductive cough, dyspnea at rest, fever, and malaise. Chest roentgenogram demonstrated bilateral diffuse interstitial and alveolar infiltration. Infectious diseases were ruled out and methotrexate-induced pneumonitis was suspected. MTX was discontinued and methylprednisolone was prescribed. Patient improved progressively. After eight weeks, radiologic abnormalities and symptoms had disappeared.