A case of allergic bronchopulmonary aspergillosis with marked peripheral blood eosinophilia successfully treated with benralizumab.

We herein report a case of allergic bronchopulmonary aspergillosis (ABPA) with marked eosinophilia and high attenuation mucus (HAM) on chest computed tomography (CT), which demonstrated a rapid and remarkable improvement with benralizumab treatment. A 67-year-old Japanese woman, who was diagnosed with asthma at the age of 64 years, was admitted with dyspnea. Her blood test results showed marked eosinophilia (peripheral blood eosinophil count 24403/μL) and elevated serum IgE levels. Chest CT also revealed ground-glass opacity. Sputum cytology detected filamentous fungi, suggesting an infection with Aspergillus spp. Based on these findings, ABPA was diagnosed. Following systemic corticosteroid treatment, her respiratory symptoms and chest radiography findings showed improvements. However, with the gradual tapering and eventual discontinuance of the corticosteroid therapy, a concomitant increase in the peripheral blood eosinophils and a recurrence of the clinical symptoms, was observed. In addition, her pulmonary function decreased and chest CT revealed worsened bronchial mucus plugs. To control the asthma with ABPA exacerbation, benralizumab was administered. Following treatment with benralizumab, the patient's asthmatic symptoms improved, together with a decrease in her peripheral eosinophil count. Mucus plugs were no longer visible on chest CT. Pulmonary function test result also showed a remarkable improvement. There was no relapse of dyspnea and no reappearance of the mucus plugs. This case suggests that benralizumab may be a suitable treatment option for patients with ABPA with marked eosinophilia and HAM on chest CT.