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Pneumoconiosis |
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Pneumoconiosis is respiratory disease caused
by inhalation of dusts.
Disease of the lungs caused by inhalation of dusts is termed 'pneumoconiosis', the majority of cases being caused by non-fibrous
mineral dusts.
Lung damage occurs when the dust interacts with defence
mechanisms in the lung.
The normal fate of inhaled dust is for it to
be coughed out of the lung or ingested into macrophages. If a dust is
toxic to macrophages, there is local inflammation, secretion of
cytokines and stimulation of fibrosis.
Fibrosis in the lung causes a restrictive pattern of respiratory
dysfunction. The main dusts causing industrial pulmonary fibrosis
are various forms of silicates, often mixed with other materials
such as iron oxide or coal.
Coalworkers' pneumoconiosis
The risk of developing coalworkers' pneumoconiosis is related to
degree of exposure to dust. There are two types of pathology.
Simple coalworkers' pneumoconiosis
is diagnosed by the presence of small nodules, 2-5 mm in diameter,
in the lung fields on chest radiograph. This pattern of disease is
not associated with any clinically significant impairment of respiratory
function.
Progressive massive fibrosis (PMF)
is characterized by large nodules in the lungs, greater than 10 mm in
diameter. The disease progresses relentlessly and may present long after
active exposure to coal dust.
Patients have severe respiratory impairment, with a mixed restrictive
and obstructive pattern.
The nodules in progressive massive fibrosis are most common in the upper lobes;
they become so extensive as
to occupy up to 30% of the lung fields. There is usually surrounding irregular
emphysema..
Histologically there is accumulation of anthracosilicotic dust in macrophages at
the centre of the
acinus, with associated emphysema of focal dust type.
There are three main pathological types of nodule in PMF:
• Caplan's syndrome occurs in miners with rheumatoid disease. The nodules have
the
appearance of large, carbon-pigmented rheumatoid nodules.
• Amorphous collection of acellular proteinaceous material containing little
collagen and abundant carbon
pigment which frequently cavitates and liquefies.
This type is seen in response to coal with a low silica content.
• Dense collagenous tissue and macrophages, heavily pigmented by carbon dust,
seen in response to coal
with high silica content.
Amorphous collection of acellular proteinaceous material containing little
collagen and abundant carbon
pigment which frequently cavitates and liquefies. This type is seen in response
to coal with a low silica
content.
Dense collagenous tissue and macrophages, heavily pigmented by carbon dust, seen
in response to coal with
high silica content. |
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