Alveolar Foamy Macrophages and Mast Cells in Bronchoalveolar Lavage of Methotrexate-induced Pneumonitis: 2 Case Reports and Review of the LiteratureD’Elia, Tommaso MD*; Mainardi, Elsa BScD†; Gandolfi, Silvia MD‡; Ghio, Loredana MD*Clinical Pulmonary Medicine: September 2013 - Volume 20 - Issue 5 - p 221–227 doi: 10.1097/CPM.0b013e3182a2dd66 Interstitial, Inflammatory, and Occupational Lung Disease Buy Abstract Author InformationAuthors Article MetricsMetrics Methotrexate-induced pneumonitis (MTX-P) is an unusual adverse drug reaction that typically manifests as an interstitial lung disease (ILD). Early diagnosis of this complication is desirable because discontinuation of MTX with or without steroid administration often results in a fast recovery. Conversely, a delay or a misdiagnosis may lead to death. Diagnostic workup is often problematic because underlying diseases leading to methotrexate administration, notably rheumatoid arthritis (RA), and opportunistic infections because of drug-induced immune impairment can also produce an ILD. In this clinical setting, bronchoalveolar lavage (BAL) plays a key role either in excluding infectious agents, especially in febrile presentations, or in looking for malignant cells. Unfortunately, BAL does not have specific features to allow clinicians to differentiate MTX-P from RA-associated ILD. Here, we present 2 definite cases of MTX-P in RA patients. BAL differential cell counts and alveolar CD4/CD8 values were found to be in agreement with those reported in the literature, but an increase in mast cells and the presence of foamy macrophages have never been reported among previously published cases. The presence of both mast cells and foamy macrophages could be helpful in differentiating MTX-P from many drug-unrelated ILDs, but does not assist in distinguishing MTX-P from Pneumocystis jiroveci pneumonia and RA-associated bronchiolitis obliterans organizing pneumonia. Departments of *Pulmonology †Clinical Pathology ‡Radiology, General Hospital of Crema, Province of Cremona, Italy The authors declare that they have nothing to disclose. Address correspondence to: Tommaso D’Elia, MD, Department of Pulmonology, General Hospital of Crema, Largo Ugo Dossena 2, Province of Cremona 26013, Italy. E-mail: email@example.com. © 2013 by Lippincott Williams & Wilkins, Inc.