Respiratory Diseases and the Fire Service

There are a number of medical conditions that can look like asbestosis,
both clinically and radiographically. A list of the most common of these
conditions is presented in Table 2-10.1. Most important of the diseases listed
are idiopathic pulmonary fibrosis (for details see the chapter on pulmonary
fibrosis) and congestive heart failure.
Most Common Conditions Mimicking Pulmonary Asbestosis
Idiopathic pulmonary fibrosis
Congestive heart failure (radiographic appearance)
Hypersensitivity pneumonitis
Scleroderma
Sarcoidosis
“Rheumatoid lung”
Other collagen vascular diseases
Lipoid pneumonia
Desquamative interstitial pneumonia
Other pneumoconioses (dust-related lung scarring)
Table 2-10.1: Common Conditions Mimicking Pulmonary Asbestosis
Pleural Thickening or Asbestos-Related Pleural Fibrosis
Pleural thickening, or asbestos-related pleural fibrosis (scarring of the lining of
the lung and/or the chest wall), is the most common consequence of exposure
to asbestos in the occupational setting. The scarring can occur in localized
areas in separate and discrete plaques (circumscribed pleural thickening) or
can occur as a more extensive and diffuse scarring process over the surface
of the pleura and involve the costophrenic angle (the angle or gutter made
by the chest wall and the diaphragm where they come together) – defined as
diffuse pleural thickening. Evidence of pleural scarring usually appears after
20 or more years have elapsed since the onset of exposure to asbestos dust
(the latency period), and a latency of 30 to 40 years after exposure begins is
not uncommon.
Under the microscope, the plaques appear as deposits of collagen, the protein
that is deposited in early scar formation. Circumscribed pleural scarring more
commonly involves the parietal pleura (the lining of the chest wall) and often
can be found on the surfaces of the diaphragm. Pleural plaques can be found on
the visceral pleura (the lining of the lung itself) as well. The pericardium (the
lining around the heart) and the pleural surfaces in the center of the chest (the
mediastinal pleura) may also be involved. Although non-calcified thickening
is more common, calcium deposits in areas of pleural scarring, whether
localized or diffused, is frequently evident on the chest x-ray and become
more common with increasing time since onset of exposure. Conditions that
can cause pleural thickening other than exposure to asbestos are presented
in Table 2-10.2.
170 Chapter 2-10 • Asbestos-Related Lung Diseases