Methotrexate induced pneumonitis

Methotrexate induced pneumonitis (MTX-P) is an uncommon, but potentially serious and life-threatening adverse event. The dose, duration of treatment and route of administration of methotrexate bear no relationship to MTX-P. Many risk factors have been studied but no definitive risk factor is identified. Pre-existing pulmonary disease may be associated with increased risk of MTX-P. Several sets of criteria have been proposed for diagnosis of MTX-P but none are validated. Diagnosis is mainly clinical and requires a high degree of suspicion. Treatment is mainly supportive along with discontinuation of methotrexate. Most patients recover. Mortality up to 17% has been reported in literature. Reintroduction of methotrexate after recovering from MTX-P is generally avoided. This article focuses on the epidemiology, clinical presentation, pathology, laboratory features and management of MTX-P.