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Pathogenesis
Two forms of asbestos fibers
1.
Serpentine – flexible and curly
2.
Amphibole – straight and brittle
Both
forms are fibrogenic but only the amphibole fibers
are associated with mesothelioma.
Another problem with asbestos is that the toxic (and
carcinogenic) chemicals that are inhaled are actually
adsorbed onto the surface of the asbestos fibers.
The
end result in release of cytokines and fibrosis.
Clinical Manisfestations
The clinical manifestations of asbestos
exposure in most people is just pleural and/or
diaphragmatic plaques.
But
you can also get:
o
Reduction in ventilatory capacity and decreased
diffusion capacity
§
This
is restrictive lung disease
o
Radiologic effects – increased interstitial markings and
pleural fibrosis and/or pleural effusion
There is also, as mentioned before, a higher risk of
developing bronchogenic carcinoma or mesothelioma. And,
again, smoking makes this risk even higher.
Morphology of Asbestosis
You
will see:
o
Diffuse pulmonary interstitial fibrosis
§
Begins in the lower lobes and subpleural areas
o
Asbestos bodies
– tiny particles of asbestos that get inhaled all the
way into your lungs that then become walled off by
macrophages.
o
Visceral pleura becomes fibrotic and adheres to chest
wall
§
This
causes more restrictive lung disease
o
Pleural and diaphragmatic plaques with calcification
§
Remember, these are pathognomonic
o
Persistent pleural effusion
Clinical Course
o
similar to any other ILD
o
symptoms appear long after exposure (> 20 years)
o
smoking greatly increases the risk of bronchogenic
carcinoma
o
development of mesothelioma (> 1000 fold risk)
The
picture below depicts asbestos bodies – they are
actually supposed to be pointed but macrophages deposits
iron on them in an attempt to wall them off so they end
up looking like dumbbells.
Their presence does not mean that you have asbestosis,
it only means that you’ve been exposed to asbestos. You
can easily hock up a loogie and get rid of them (great
image, I know).
This
picture shows asbestos related ILD. You can see the area
of fibrosis in pink surrounded by areas of the lung that
are unaffected. If this happens all over the lung, you
will get restrictive lung disease.
This
picture above is of asbestos related mesothelioma,
tumor of the pleura. It eventually invades the
lung and slowly suffocates the patient. In this picture,
it has invaded the septa.
The
picture above is a histological slide of the same
mesothelioma. Although, grossly, the mesothelioma looks
like other typical adenocarcinomas of the lungs,
histologically it is different.
Berylliosis
-
Associated with aerospace, nuclear, and electronic
equipment
-
Acute Berylliosis
o
Chemical pneumonitis with interstitial edema,
inflammation, and epithelial cell reaction
o
May
be fulminant (sudden and intense) and result in death
o
May
regress completely
o
May
progress to chronic berylliosis
-
Chronic Berylliosis
– this is what you usually see
o
Intersitial fibrosis and pleural fibrosis are seen
o
You
will see non-caseating granulomatas with bifringent
calcite bodies (Schaumann’s bodies)
§
So,
not all granulomas are due to infections such as TB.
o
Histology is similar to a sarcoid
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