Chest
Volume 94, Issue 6, December 1988, Pages 1309-1311
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Selected Reports
Epithelial Necrosis and Alveolar Collapse in the Pathogenesis of Usual Interstitial Pneumonia

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We report ultrastructural evidence of epithelial necrosis and alveolar collapse in a patient with usual interstitial pneumonia (UIP). These changes were focal and confined to small areas characterized histologically by aggregates of interstitial fibroblasts embedded within a myxoid stroma (fibroblastic foci). Ultrastructurally, the denuded epithelial basal lamina in these areas showed deep infoldings into the interstitium, and the luminal surfaces of the resultant clefts often were re-epithelialized. These findings suggest that the fibroblastic foci commonly seen in UIP represent sites of acute lung injury, and that alveolar collapse following epithelial necrosis is an important mechanism of lung remodeling. In addition to new insights regarding the pathogenesis of fibrosis in UIP, these observations may have important implications for assessing prognosis and selecting treatment strategies. (Chest 1988; 94:1309-11)

Section snippets

CASE REPORT

A 68-year-old white man was referred to our institution for evaluation of increasing dyspnea. Physical examination revealed diffuse rales bilaterally and there was clubbing of his fingers and toes. A chest roentgenogram showed coarse reticular opacities throughout both lungs associated with moderate volume loss. He underwent thoracotomy with biopsy of the left upper lobe. The lung biopsy specimen was routinely processed for light and electron microscopy.

Light Microscopy

The lung showed typical histologic features of UIP characterized by a variegated low magnification appearance in which relatively normal lung alternated with zones of interstitial inflammation, fibrosis, and honeycomb change. The areas of interstitial fibrosis consisted mainly of end-stage, mature fibrosis with dense collagen deposition. There were also scattered small foci containing less mature fibrosis composed of aggregates of loosely clustered fibroblasts dispersed in a faintly basophilic,

Discussion

The findings in our case suggest that epithelial necrosis and alveolar collapse are important in the pathogenesis of UIP. The epithelial necrosis is confined to small foci that are widely scattered and recognized histologically by the presence of loosely aggregated interstitial fibroblasts (fibroblastic foci). Similar areas can be found in most examples of UIP.2, 4 Alveolar collapse also occurs in the fibroblastic foci and likely results from the epithelial necrosis. Ultrastructurally, alveolar

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