Hypereosinophilic obliterative bronchiolitis: a distinct, unrecognised syndrome

Biopsy-proven cases of eosinophilic bronchiolitis have only been reported in isolation, and all come from Japan. We present six patients with hypereosinophilic obliterative bronchiolitis (HOB), defined by the following criteria: 1) blood eosinophil cell count >1 G·L(-1) and/or bronchoalveolar lavage eosinophil count >25%; 2) persistent airflow obstruction despite high-dose inhaled bronchodilators and corticosteroids; and 3) eosinophilic bronchiolitis at lung biopsy (n=1) and/or direct signs of bronchiolitis (centrilobular nodules and branching opacities) on computed tomography (n=6). Chronic dyspnoea and cough which was often severe, without the characteristic features of asthma, were the main clinical manifestations. Atopy and asthma were present in the history of three and two patients, respectively. One patient met biological criteria of the lymphoid variant of idiopathic hypereosinophilic syndrome. Mean blood eosinophil cell count was 2.7 G·L(-1) and mean eosinophil differential percentage at bronchoalveolar lavage was 63%. Mean initial forced expiratory volume in 1 s/forced vital capacity ratio was 50%, normalising with oral corticosteroid therapy in all patients. HOB manifestations recurred when oral prednisone was decreased to 10-20 mg·day(-1), but higher doses controlled the disease. HOB is a characteristic entity deserving to be individualised among the eosinophilic respiratory disorders. Thorough analysis is needed to determine whether unrecognised and/or smouldering HOB may further be a cause of irreversible airflow obstruction in chronic eosinophilic respiratory diseases.