Page 509 - Textbook of Pathology, 6th Edition

3. There may be changes of emphysema in the principally used in nuclear and aerospace industries and in 493
pulmonary parenchyma between the areas of interstitial the manufacture of electrical and electronic equipments. Two
fibrosis. forms of pulmonary berylliosis are recognised—acute and
4. The involvement of hilar lymph nodes in asbestosis is chronic.
not as significant as in silicosis. ACUTE BERYLLIOSIS. Acute berylliosis occurs in

B. PLEURAL DISEASE. Pleural disease in asbestos individuals who are unusually sensitive to it and are heavily
exposure may produce one of the following 3 types of exposed to it for 2 to 4 weeks. The pulmonary reaction is in
lesions: the form of an exudative chemical pneumonitis in which the
alveoli are filled with protein-rich fluid with formation of
1. Pleural effusion. It develops in about 5% of asbestos
workers and is usually serious type. Pleural effusion is hyaline membrane. The patient develops sudden dyspnoea,
generally accompanied by subpleural asbestosis. hyperapnoea and substernal pain. Most patients recover
completely.
2. Visceral pleural fibrosis. Quite often, asbestosis is
associated with dense fibrous thickening of the visceral CHRONIC BERYLLIOSIS. Chronic berylliosis develops in
pleura encasing the lung. individuals who are sensitised to it for a number of years,
often after a delay of 20 or more years. The disease is a cell-
3. Pleural plaques. Fibrocalcific pleural plaques are the
most common lesions associated with asbestos exposure. mediated hypersensitivity reaction in which the metal
Grossly, the lesions appear as circumscribed, flat, small beryllium acts as a hapten. The condition is characterised by
(upto 1 cm in diameter), firm or hard, bilateral nodules. development of non-caseating epithelioid granulomas like
They are seen more often on the posterolateral part of those of sarcoidosis. These granulomas are diffusely scattered
parietal pleura and on the pleural surface of the throughout the lung parenchyma. The granulomas have
diaphragm. giant cells which frequently contain 3 types of inclusions:
Microscopically, they consist of hyalinised collagenous 1. Birefringent crystals.
tissue which may be calcified so that they are visible on 2. Concentrically-laminated haematoxyphilic Schaumann or
chest X-ray. Asbestos bodies are generally not found conchoid bodies.
within the plaques. 3. Acidophilic stellate-shaped asteroid bodies. CHAPTER 17
These inclusions are described in giant cells of
C. TUMOURS. Asbestos exposure predisposes to a granulomas in sarcoidosis too (Chapter 6). Similar sarcoid-
number of cancers, most importantly bronchogenic like granulomas can occur in other organs such as in the liver,
carcinoma (page 496) and malignant mesothelioma (page kidneys, spleen or lymph nodes in chronic berylliosis.
505). A few others are: carcinomas of oesophagus,
stomach, colon, kidneys and larynx and various lymphoid ILD ASSOCIATED WITH IMMUNOLOGIC LUNG DISEASES
malignancies.
1. Bronchogenic carcinoma is the most common Hypersensitivity (Allergic) Pneumonitis
malignancy in asbestos workers. Its incidence is 5 times
higher in non-smoker asbestos workers than the non- Hypersensitivity pneumonitis is a group of immunologically- The Respiratory System
smoker general population and 10 times higher in smoker mediated ILDs occurring in workers inhaling a variety of
asbestos workers than the other smokers. organic (biologic) antigenic materials. The condition may
have an acute onset due to isolated exposure or may be chronic
2. Malignant mesothelioma is an uncommon tumour due to repeated low-dose exposure.
but association with asbestos exposure is present in 30 to
80% of cases with mesothelioma. The exposure need not ETIOPATHOGENESIS. A list of important organic
be heavy because mesothelioma is known to develop in (biologic) dusts which may be inhaled to produce hyper-
people living near asbestos plants or in wives of asbestos sensitivity pneumonitis is already given in Table 17.9. The
workers. immunologic mechanisms underlying hypersensitivity
pneumonitis from any of these causes appear to be either
CLINICAL FEATURES. Asbestosis is a slow and insidious type III immune-complex disease or type IV delayed-
illness. The patient may remain asymptomatic for a number hypersensitivity reaction.
of years in spite of radiological evidence of calcific pleural 1. Farmers’ lung is the classic example resulting from
plaques and parenchymatous changes. However, onset of exposure to thermophilic actinomycetes generated by humid
interstitial fibrosis brings about dyspnoea with dry or and warm mouldy hay.
productive cough. More advanced cases show development 2. Bagassosis occurs in individuals engaged in manufacture
of Caplan’s syndrome, pulmonary hypertension, cor of paper and cardboard from sugarcane bagasse. Spores of
pulmonale and various forms of cancers. thermophilic actinomycetes grow rapidly in mouldy
sugarcane bagasse which are inhaled.
Berylliosis
3. Byssinosis is an occupational lung disease occurring in
Berylliosis is caused by heavy exposure to dust or fumes of workers exposed to fibres of cotton, flex and hemp for a
metallic beryllium or its salts. Beryllium was used in the past number of years. The role of immunologic mechanisms in
in fluorescent tubes and light bulbs but currently it is byssinosis is not as clear as in exposure to other organic dusts.