A 27-year-old woman presents with severe shortness of breath, coughing, and wheezing. She is initially nonresponsive because of the severity of her symptoms. After administration of inhaled corticosteroids, her symptoms improved. The patient has had asthma since childhood but is finding her symptoms increasingly hard to control despite use of inhaled corticosteroids and bronchodilators. A chest radiograph yields normal findings. Eosinophil count is 450 cells/µL.