Methotrexate-induced pneumonitis: heterogeneity of bronchoalveolar lavage and differences between cancer and rheumatoid arthritis.

PURPOSE Our knowledge on bronchoalveolar lavage (BAL) of methotrexate-induced pneumonitis (MTX-P) is fragmentary and based on data that are sometimes apparently conflicting. Aim of this review was to provide a comprehensive overview on the BAL features of MTX-P arising from cases published to date, and to determine the cytological patterns and any differences between cancer and rheumatoid arthritis patients, the two patient subsets among which this complication more often occurs. METHODS English-language articles published up to November 2013 were systematically searched through PUBMED, EMBASE, and other databases. Adult patients with a proven diagnosis of MTX-P and careful mention of each BAL parameter were examined. RESULTS Seventeen articles for a total of 47 patients were included. Four BAL patterns with a variably combined lymphocytosis and two with prominent neutrophilia were identified. A more intense lymphocytosis (P=0.004) and a more depressed CD4/CD8 ratio (P=0.01) were found in cancer patients compared with rheumatoid arthritis patients. CONCLUSIONS In MTX-P, cytological analysis of BAL may disclose up to six different patterns. In MTX-P affecting cancer patients, BAL tends to show the typical features of hypersensitivity pneumonitis, while, in rheumatoid arthritis patients, it is more heterogeneous, with a less intense lymphocytosis, a more pronounced neutrophilia, and a higher CD4/CD8 ratio. These differences could be related to a disparity in baseline pulmonary conditions between the two background diseases, i.e., to the presence of previously healthy lungs in cancer patients, and lungs already involved by the immune-mediated inflammatory processes, often not manifestly, in rheumatoid arthritis patients.