elastin and Asbestosis

Asbestosis has long been defined as a diffuse interstitial "fibrotic" process, in similarity to other chronic interstitial pulmonary diseases. To address the hypothesis (which was based on morphological nuances) that the interstitial connective tissue response in asbestosis may be fibroelastotic rather than fibrotic, a comparative characterization of the connective response in cases of asbestosis and other forms of interstitial lung disease was performed. Archival open lung biopsies or autopsy specimens of pulmonary diseases featuring interstitial connective tissue abnormalities (15 of asbestosis, 21 of organizing pneumonia, 15 usual interstitial pneumonitis/idiopathic pulmonary fibrosis [IPF], 9 organizing diffuse alveolar damage, 9 "nonspecific" interstitial pneumonitis, 4 sarcoidosis, 3 each of desquamative interstitial pneumonia and chronic amiodarone toxicity, 2 cryptogenic organizing pneumonias, and 1 each of chronic hypersensitivity pneumonitis and chronic eosinophilic pneumonitis [85 total]) were stained histochemically with hematoxylin and eosin, Perl's method, Gomori's trichrome procedure, and the Verhoeff-van Gieson technique. Representative subsets of the cases (n = 20) were also studied immunohistologically using an antibody to elastin. Fibroelastosis in each of the samples was assessed for the degree of response and its location using a 3-tiered scale. The degree of fibroelastosis in the 15 cases of asbestosis was variable, with the pattern being peribronchial and perivascular in all instances; at least 2 asbestos bodies were identified in fibroelastotic foci in each of the 15 cases as highlighted with Perl's stain. Forty-seven cases of nonasbestotic lung disease (71%) showed interstitial fibrosis with a variable (usually modest) amount of admixed elastic tissue; when present, elastic fibers were distributed in a diffuse interstitial pattern, with or without perivascular accentuation. All cases of IPF also showed areas of fibroelastosis, but those foci were confined to regions of overt "honeycomb" change. No asbestos bodies were seen in any disease except asbestosis, and a predominantly peribronchial pattern of fibroelastosis was not identified in any nonasbestotic interstitial lung disease in this study. The authors conclude that the types and patterns of pulmonary connective tissue response in interstitial lung diseases may provide additional diagnostic clues to the presence of asbestosis.

Topics: Adult; Aged; Asbestosis; Biomarkers; Connective Tissue; Elastic Tissue; Elastin; Female; Fibrosis; Humans; Idiopathic Pulmonary Fibrosis; Immunohistochemistry; Lung Diseases, Interstitial; Male; Middle Aged; Pilot Projects

Lung biopsies from 17 patients with cryptogenic fibrosing alveolitis of a cellular rather than fibrotic pattern were examined by transmission electron microscopy in the hope that such cases would show features of pathogenetic significance. Further selection was made by choosing minimally affected areas. There was no ultrastructural evidence of immune complex deposition but alveolar epithelial and capillary damage was frequently found (17 and 14 of the 17 cases respectively). Alveolar epithelial injury consisted of patchy necrosis and regenerative hyperplasia. Alveolar capillary injury consisted of cytoplasmic swelling and basement membrane thickening and reduplication. Many of these features have not been emphasized in previous reports and their prominence in early stages of the disease suggest that they may have pathogenetic significance, possible mechanisms of which are discussed. Similar findings identified during the course of this study in 8 asbestos workers suggest that similar pathogenetic mechanisms may operate in asbestosis.

Topics: Asbestosis; Basement Membrane; Capillaries; Collagen; Elastin; Humans; Lung; Microscopy, Electron; Pulmonary Alveoli; Pulmonary Fibrosis