A case of follicular bronchiolitis associated with asthma, eosinophilia, and increased immunoglobulin E

A 49-year-old woman, who had been diagnosed with asthma, showed a bilateral diffuse pattern of small centrilobular nodules on CT. Laboratory data revealed peripheral eosinophilia and a marked increase in total serum IgE levels. The nodules detected on CT were initially considered to be associated with bronchiolar infiltration of eosinophils. Pathological findings from thoracoscopy revealed infiltration of eosinophils into the airway lumen and walls, goblet cell hyperplasia, and thickening of the basement membrane in large bronchi, consistent with asthma. However, hyperplastic lymphoid follicles with reactive germinal centers were observed along the bronchioles. The follicles had no evidence of monoclonality suggested by immunohistological analysis, and no remarkable infiltrates of eosinophils, suggesting follicular bronchiolitis (FB). After treatment with prednisolone, the small diffuse nodules improved markedly, and peripheral eosinophilia and total serum IgE levels also decreased. To the best of our knowledge, this is the first documented case report of FB associated with asthma, eosinophilia, and elevated IgE with a definite pathophysiological diagnosis.