C.S. Glaze , L.S. Newman / Clin Chest Med 25 (2004) 467–478
Table 2 Inorganic fibrous dust pneumoconiosis
Select exposure scenarios
Well described Asbestos
Construction trades, building maintenance, mining, milling, production of asbestos products, shipbuilding and repair, automobile and railroad work, electrical wire insulation, as a contaminant in talc or vermiculite
Lower zone predominant reticular opacity, honeycombing; associated pleural disease is common
Less well characterized Palygorskites (attapulgite
and sepiolite) Wollastonite
Silicon carbide (carborundum)
Aluminum oxide Nylon flock
Fuller’s earth, paint thickeners, drilling mud, asbestos substitute Mining and milling, asbestos substitute, ceramics Environmental exposure
Abrasive, refractory materials, ceramics, metal matrix composites
Aluminum oxide abrasives manufacture Production of nylon flock (especially the random-cut method)
Lower zone predominant reticular opacity
Lower zone predominant reticular opacity; may have associated pleural plaques Lower zone predominant reticular opacity; may have associated pleural plaques Upper zone predominant reticulonodular infiltrates; may have associated hilar prominence Diffuse irregular interstitial markings CT findings — ground-glass attenuation and micronodules; reticular opacity and consolidation also may be seen
Adapted from Begin R. Asbestos. In: Harber P, Schenker M, Balmes J, editors. Occupational and environmental respiratory disease. St. Louis: CV Mosby; 1996. p. 293– 320; Lockey J. Man-made fibers and nonasbestos fibrous silicates. In: Harber P, Schenker M, Balmes J, editors. Occupational and environmental respiratory disease. St. Louis: CV Mosby; 1996. p. 330– 44; with permission.
finding [34,39,40]. Direct measures of gas exchange by arterial blood gases, especially during exercise testing, provide the most sensitive indication of physiologic impairment.
The radiographic features of asbestosis are well described. A chest radiograph typically reveals bilat- eral predominant irregular or reticular opacities at the lung bases. Honeycomb change occurs in advanced cases. Presence of bilateral pleural plaques increases the confidence with which one makes the diagnosis, as does a slow rate of radiographic progression of interstitial opacities. High-resolution CT (HRCT) is more sensitive than plain chest radiography for the detection of asbestosis [41 – 43]. HRCT findings include thickened interlobular septal lines and intra- lobular core structures (with the latter being the initial or earliest CT abnormality), curvilinear lines that persist in the prone position, subpleural ground-glass attenuation, and honeycombing . These changes correlate with pathologic findings . Parenchymal fibrous bands are also seen but correlate better with diffuse pleural thickening . The CT changes are located primarily in the basilar and subpleural regions . The presence of concomitant pleural disease is an important clue to differentiating asbestosis from IPF. Pleural disease is rare in IPF, but more than 90%
of patients with asbestosis show some pleural abnor- mality (plaques, diffuse thickening, or both) on HRCT . The percentage of patients with concomi- tant pleural disease visible on chest radiography is significantly lower, however [40,48].
Asbestosis is diagnosed according to previously discussed principles. The primary industries associ- ated with exposure risk are shown in Table 2. When bi- opsies are performed, the presence of asbestos bodies or performing fiber counts can assist in the diagnosis. There are published standards for interpretation, but there is significant variability among laboratories [22,34,49]. The pathologic lesion of asbestosis begins with a peribronchiolar fibrosis, which extends into surrounding alveolar walls. As the disease progresses, the pathology is similar to UIP, and the severity can be graded according to published schemata . Al- though the presence of asbestos bodies on biopsy can help if they are present, many biopsies of as- bestosis do not show these abnormalities because of sampling error and the size of biopsies. A diagno- sis never should be excluded just because asbestos bodies were not observed. Biopsies are not commonly needed to diagnosis asbestosis, because a reasonable diagnosis can be made in most cases based on chest radiography or CT scan, compatible clinical and