The patient's clinical course, before and after mepolizumab treatment. Changes in the patient's blood eosinophil count, serum IgE level, dose of oral prednisolone and inhalation of budesonide/formoterol (BUD/FM), forced expiratory volume in one second (FEV1), forced expiratory volume % in one second (FEV1%), and fractional exhaled nitric oxide (FeNO) level. After the mepolizumab treatment (100 mg/4 weeks), the blood eosinophil count dropped from 276/μL to 20/μL, the serum IgE level dropped from 4,970 IU/L to 2157 IU/L, and the FeNO level dropped from 67 ppb to 39 ppb.