A case of protracted bacterial bronchitis successfully treated with low-dose macrolide therapy after long-term management as bronchial asthma

Abstract

Protracted bacterial bronchitis (PBB) is a leading cause of chronic wet cough in children but is often misdiagnosed as bronchial asthma. A 9-year-old girl presented with a 5-year history of persistent wet cough. She had been treated for asthma with high-dose inhaled corticosteroids without improvement. Examination revealed squawks and rhonchi. Investigations showed low fractional exhaled nitric oxide (5 ppb), no airway reversibility, and 98％ neutrophils in sputum. Chest CT demonstrated centrilobular opacities and bronchial wall thickening. Suspecting a pathology similar to diffuse panbronchiolitis (DPB), low-dose clarithromycin (CAM) was initiated. Symptoms vanished within one week, and radiological findings resolved within six months. The patient was finally diagnosed with PBB based on the clinical course. She remained symptom-free for 30 months after treatment cessation. In the present case diagnosed with PBB retrospectively, the anti-inflammatory and anti-hypersecretory effects of macrolides were considered effective against the pathology characterized predominantly by neutrophilic inflammation. In Japan, where low-dose macrolide therapy is frequently employed for chronic wet cough, PBB may be an underlying condition. Furthermore, it is crucial to consider PBB as a differential diagnosis in cases of wet cough refractory to asthma treatment.