Methotrexate-induced asthma.

A patient with rheumatoid arthritis developed pulmonary symptoms and function test abnormalities consistent with asthma during methotrexate therapy. Assessments of airway responsiveness to methacholine during therapy revealed airway hyperreactivity that reverted to normal when the methotrexate was stopped. An extension of the methotrexate dosage interval from 7 to 10 days resulted in an abolition of the asthma, which remained in remission despite a return to a weekly cycle after a 3-month period of 10-day cycles.