Methotrexate pneumonitis is characterized by dyspnea, non productive cough, fever and hypoxemia. Peripheral eosinophilia is frequently present. Early in the disease the chest radiograph demonstrates interstitial infiltrates after progressing to an alveolar filling pattern which clears rapidly in most cases. However, radiographic and pulmonary function test abnormalities may persist chronically after methotrexate is discontinued. The histopathologic features include interstitial and alveolar infiltrates of round cells. Granulomas and interstitial fibrosis have been noted in some cases. The precise manner in which methotrexate induces pulmonary disease is not known but both allergic and cytotoxic etiologies have been suggested. Corticosteroid therapy favors recovery, although 11% of cases reported in the literature of cases have died in the acute phase, indicating that methotrexate therapy may lead to severe complications (95 references).
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