Membranous obliterative bronchitis: a proposed unifying model.

Three adults with cystic fibrosis (one after lung transplantation) presented with fever, chest pain, and acute radiographic changes. The changes included a cavitary lesion of the lung, acute dense infiltrates, and lobar collapse. After failing conventional antibiotic therapy, the patients underwent flexible bronchoscopy. All had bronchial obstruction by a membrane that had completely occluded the bronchial orifice at the bifurcation of the bronchi. Therapeutic interventions ranged from continuing intravenous antibiotics, bronchoscopy-assisted perforation of the membrane by sharp instrumentation, and transthoracic needle-guided perforation of the membrane with subsequent stenting of the orifice. The patients recovered, but the posttransplant patient had recurrent membranous obstructions with multiple interventions. The cause and triggers of the process are unknown. Based on repeated observations of the evolution of the membranes, and histologic material from bronchoscopies, we propose a putative paradigm of the natural history of the process. We suggest that local stimuli generate a richly vascularized granulation polyp, which progresses in a "shutter-like" motion to form partial or completely obstructive membranes. The subsequent course depends on the vascular supply to the membrane. We also propose that similar processes may be the underlying pathologic events in some cases of lung abscess and necrotizing pneumonia.