Asbestosis
Asbestosis can manifest as pleural or parenchymal fibrosis or both. Pleural
asbestosis, more properly termed “asbestos-related pleural abnormalities,”
is the most common finding in asbestos-induced pulmonary disease and, as
described previously, involves pleural thickening, often manifested as
discrete pleural plaques. Pleural plaques can be seen radiologically as
bilateral images of hyalin scar formation on either the visceral or, much more
commonly, the parietal pleural surfaces. The specificity of pleural plaques is
low on radiographs unless the plaques are well defined. The most common
differential diagnosis is subpleural fat. Well-defined asbestos-related pleural
plaques on radiographs include bilateral circumscribed plaques, bilateral
calcification, and diaphragmatic plaques. Pleural plaques rarely cause
symptoms. Diffuse pleural fibrosis, seen as visceral pleural thickening, can
be associated with mild or, rarely, moderate or severe restrictive pulmonary
defects, with dyspnea and restrictive changes on pulmonary function tests.
There can be a benign pleural effusion.
A patient with parenchymal asbestosis commonly develops fatigue, weight
loss, and insidious onset of dyspnea on exertion. As the disease progresses,
the dyspnea worsens, regardless of any further asbestos exposure. A dry
cough typically occurs, but a productive cough, even in a nonsmoker, is not
uncommon. Patients often describe a “tight” feeling in the chest. Common
findings are bibasilar fine end-inspiratory crackles (32% to 64%) and
clubbing of the fingers (32% to 42%) (which occurs at a later stage of the
disease). In the advanced stages of the disease, signs of cor pulmonale are
common. Functional disturbances can include gas exchange abnormalities
(e.g., diffusing capacity), a restrictive pattern, and obstructive features due
to small airway disease (International Expert Meeting on Asbestos,
Asbestosis, and Cancer 1997). The interstitial disease is radiographically
demonstrated as a reticular fibrosis located predominantly in the lower lung
fields. Radiologic evidence is often not present until at least 5 years after
exposure. The American Thoracic Society states that there is convincing
evidence that an asbestos-related pulmonary abnormality can occur in the
absence of definite radiologic change (American Thoracic Society 1986).
The detection of asbestosis by standard films (chest radiography) should be
guided by standard reading methods such as those of the International
Labour Organization (ILO) classification system and read by certified
B readers trained to use this classification system. Early changes not seen on
chest radiography can be found using HRCT in selected cases.
Fibrosis found symmetrically in the lower aspects of both lungs is typically
caused by asbestos. Fibrotic lung disease due to asbestos inhalation is often
associated with pleural plaque formation, which eliminates other etiologic
possibilities such as drugs; radiation; sarcoidosis; collagen vascular
• Progressive dyspnea on
exertion is a common symptom
of asbestosis.
• Significant clinical syndromes
include asbestosis, lung cancer,
and mesothelioma.
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