Eosinophilic bronchiolitis successfully treated with benralizumab

A 53-year-old non-smoking Japanese woman was admitted to our hospital with a 20-year history of wet cough and dyspnoea on exertion. Bronchial asthma (BA) had been diagnosed 20 years earlier. Although she has been treated with high-dose inhaled corticosteroid, she had experienced frequent exacerbation of BA, and short-term oral corticosteroid bursts were occasionally administered. High-resolution CT of the chest revealed diffuse centrilobular nodules with bronchial wall thickening and patchy ground-glass opacities in both lungs. Lung biopsy specimens showed widespread cellular bronchiolitis with follicle formations in the membranous and respiratory bronchioles, accompanied by marked infiltration of plasma cells and eosinophils. In addition, immunohistochemical immunoglobulin G4 (IgG4) staining revealed many IgG4-positive plasma cells, and the ratio of IgG4-positive cells to IgG-positive cells exceeded 40%. The final diagnosis was eosinophilic bronchiolitis with marked IgG4-positive plasma cell infiltration in association with BA. With benralizumab therapy, her clinical condition dramatically improved.