Abstract
A 32 year old man with chronic severe asthma, requiring maintenance oral corticosteroids, was started on a weekly dose of methotrexate. Eleven weeks later he developed Pneumocystis carinii pneumonia. In the two years following treatment there has been no recurrence while oral corticosteroid treatment has been continued. Pneumocystis pneumonia should be considered in asthmatic patients taking methotrexate who present with fever, pulmonary infiltrates, and hypoxia.