Methotrexate Induced Pneumonitis: A Review Article

Low dose methotrexate (MTX) is used frequently in a wide variety of conditions. This includes rheumatological conditions such as rheumatoid arthritis (RA) and non-rheumatological conditions such as inflammatory bowel disease. One of the most serious although infrequent side effects of low dose MTX is MTX induced pneumonitis (MTX-P). The latest literature on epidemiology, risk factors, pathophysiology and clinical features of MTX-P will be critically reviewed and highlighted. This review will pay special attention to diagnostic criteria, high resolution computerised tomography (HRCT) scan findings, and when to consider bronchoalveolar lavage (BAL) and lung biopsy. We propose the 2008 diagnostic criteria adapted from existing criteria. We will also discuss the new issue of interstitial lung disease (ILD) in patients receiving both methotrexate and anti-TNF therapy.