Diffuse Panbronchiolitis

Diffuse panbronchiolitis is an idiopathic chronic progressive inflammatory disease characterized by transmural inflammation (panbronchiolitis) of respiratory bronchioles affecting both lungs diffusely. The histopathology shows infiltration of the bronchiolar walls by lymphocytes, plasma cells, and foamy macrophages, with peribronchiolar accumulation of foamy macrophages and lymphocytes. The disease was first described in Japan in 1960s and remains predominantly an East Asian disease (Japan, Korea, China, Taiwan), with strong HLA associations (HLA-B54 in Japanese, HLA-A11 in Koreans).

Clinical presentation typically begins in 4th-5th decade with chronic sinusitis (90%, often preceded by other symptoms by years), chronic productive cough with copious purulent sputum, exertional dyspnea, weight loss, and recurrent respiratory infections. Pulmonary function shows obstructive ventilatory defect with hypoxemia. Sputum cultures often show Pseudomonas aeruginosa colonization in advanced disease. Without treatment, progression leads to extensive bronchiectasis, respiratory failure, and death.

Diagnosis based on clinical criteria (chronic productive cough, sinusitis, characteristic HRCT findings showing diffuse small centrilobular nodules with tree-in-bud opacities and bronchiolectasis predominantly in lower lobes), with confirmatory lung biopsy in atypical cases. Treatment with long-term low-dose macrolides (erythromycin 400-600 mg/day or azithromycin 250-500 mg 3x/week) revolutionized DPB prognosis. The mechanism is anti-inflammatory and immunomodulatory rather than antibacterial. Treatment continues 2+ years; relapses can occur after stopping. 5-year survival increased from 25% (pre-macrolide) to >90% (post-macrolide era).