A retrospective study of bronchial hyperresponsiveness in patients with asthma before the onset of Churg–Strauss syndrome

Asthma is one of the most common clinical symptoms in Churg–Strauss syndrome (CSS). However, it is not known how lung function and bronchial hyperresponsiveness (BHR) prior to the development of CSS differs from asthmatics do not develop CSS. This retrospective cohort study was conducted to predict the onset of CSS and facilitate diagnosis in the early phase of the disease. We examined 24 pre-CSS asthmatic patients and 294 non-CSS asthmatic patients for clinical features, percent forced expiratory volume at 1 second (%FEV₁), BHR to acetylcholine, and evaluated eosinophils (%) in the peripheral blood at their first hospital visit for asthma treatment. All of the 24 pre-CSS patients had adult-onset asthma. The asthma of 87.5% of pre-CSS patients at the first hospital visit before the onset of CSS was severe and was complicated by sinusitis. The eosinophils (%) in the peripheral blood was significantly higher than in non-CSS asthmatic patients. The %FEV₁ in both the patients with severe asthma and the patients who developed CSS was lower than in patients with mild or moderate asthma. However, BHR in pre-CSS patients was significantly better than in non-CSS patients with severe asthma and was as mild as in patients with mild asthma. Patients who developed CSS had clinically severe asthma before the onset of CSS. The severity of their asthma was related to airflow limitation and eosinophilic inflammation in the peripheral blood, but not to BHR. These findings should prove useful in future early diagnosis and treatment of CSS.