Diffuse panbronchiolitis

Diffuse panbronchiolitis (DPB) is a chronic inflammatory lung disease that primarily affects the respiratory bronchioles — the smallest airways in the lungs. The condition is characterized by progressive inflammation centered around the bronchioles, leading to chronic cough, large volumes of purulent (pus-containing) sputum production, and exertional dyspnea (shortness of breath during physical activity). Patients frequently develop chronic sinusitis, and the combination of upper and lower airway disease is a hallmark of DPB. The disease predominantly affects individuals of East Asian descent, particularly Japanese, Korean, and Chinese populations, suggesting a strong genetic susceptibility component linked to certain HLA (human leukocyte antigen) haplotypes, notably HLA-B54 in Japanese populations and HLA-A11 in Korean populations. If left untreated, diffuse panbronchiolitis progresses to bronchiectasis (permanent dilation and damage of the airways), recurrent respiratory infections — often with Pseudomonas aeruginosa — and ultimately respiratory failure. Pulmonary function tests typically show an obstructive pattern with reduced forced expiratory volume. Chest imaging reveals characteristic diffuse small centrilobular nodular opacities, often described as a 'tree-in-bud' pattern on high-resolution CT scanning. The prognosis of DPB was historically very poor, with five-year survival rates as low as 25–50% before effective treatment was identified. The treatment landscape for DPB was revolutionized by the discovery that long-term, low-dose macrolide antibiotic therapy — particularly erythromycin administered at 400–600 mg daily for at least six months and often longer — dramatically improves symptoms, pulmonary function, and survival. This macrolide therapy works primarily through anti-inflammatory and immunomodulatory mechanisms rather than direct antibacterial effects. Since the introduction of macrolide therapy, the ten-year survival rate has improved to over 90%. Azithromycin and clarithromycin are also used as alternatives. Supportive care may include bronchodilators, mucolytics, and treatment of secondary bacterial infections.

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