|Print Date:||March 12, 2014, 4:12 am|
|Text||Asbestos is a general term used to describe fibers created from hydrated magnesium silicates. There are two types of fibers, serpentines and amphiboles. Chrysotile, a type of serpentine fiber, is the main fiber used commercially in the U.S. and is considered less toxic than the amphiboles fibers. Exposure occurs through the mining and milling of fibers (primary exposure), application of asbestos (secondary exposure), or through nonoccupational exposure to aerosolized fibers. Secondary exposure is the most clinically significant.
Asbestos causes three diseases: asbestosis, lung cancer, and mesothelioma. A clear association exists between increased risk of cancer in exposed smokers. Most patients are asymptomatic for 20-30 years following exposure. The risk of developing disease and severity are proportional to the degree of exposure. Dyspnea on exertion is usually the earliest clinical manifestation. PFTs will demonstrate a restrictive pattern with reduced lung volumes and decrease compliance without evidence of airway obstruction.
Pathologically, disease begins with the inhalation of fibers, which become trapped in lower airways. There, they damage epithelial cells and macrophages, which initiates an inflammatory cascade resulting in alveolitis. If the asbestos burden is high, this cascade may ultimately lead to collagen deposition and progressive fibrosis.
On plain films, disease is manifested by a reticular interstitial process within the lower lung zones with bilateral mid-lung zone pleural plaques. The pleural plaques are a hallmark of asbestosis and usually spare the lung apices and costophrenic angles. As disease progresses, there is coarsening of the interstitium with honeycombing. Common findings on high-resolution CT include: intralobular small rounded or branching opacities, thickened interlobular septa, subpleural curvilinear lines, and parenchymal bands. Coarse honeycombing is seen in advanced disease. The subpleural lower lungs are most prominently affected.
|References:||Chun, S. Asbestosis. www.emedicine.com. 2004.
Dahnert, W. Radiology Review Manual. 4th ed. 2000.
King, TE. Asbestosis. www.uptodate.com. 2006
Rubin, E, et al. Rubin\\\\\\\'s Pathology. 4th ed. 2005.
|Contributor||Michael V Huppmann (Walter Reed Army Medical Center)|
|Peer Reviewer||Ernesto Torres M.D. (Civilian Medical Center)|
|Record Number||: 7259|
|Location:||Chest, Pulmonary (ex. Heart)|
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