One may well ask what are the various types of Asbestos related diseases and why there should be a difference in behavior between different types of asbestos. Several factors are involved, the most important being fiber size; long thin fibers, usually amphiboles, are the most dangerous.
[Why that is] is still controversial. Processing alters fibers and we can recognize those industries in which workers are at less risk, probably due to changes in the fibrous form. Knowledge of which local industries used asbestos in the past can be of great help to a GP…”
In this country, commmon asbestos related diseases are pleural thickening and plaques, asbestos pleurisy with effusion, interstitial lung disease, carcinoma of the lung, and mesothelioma of the pleura and peritoneum. The severity of the disease may reflect the degree of exposure.
Pleural plaques occur in groups who have had moderate exposure to asbestos. if the plaques calcify, more likely on the diaphragm then visualization is easier. Pleural thickening can be more irregular and is even more difficult to see. Advanced cases have a ‘crows’ feet‘ configuration running across the chest X-ray.
Clinical presentation is varied, eg plaques may be found by chance or they may be found in a patient presenting with lung cancer. They are useful markers of exposure. Plaques are less likely than diffuse pleural thickening to be associated with underlying interstitial [between parts i.e. connective tissue] disease.
On their own plaques cause virtually no disturbance of lung function and neither are they thought to be direct precursors of pleural mesothelioma.
Pleural plaques are areas of scarring found on pleural surface lining wail. Usually bilateral and symmetrical; large areas of scarring also found on the diaphragm. Vary in size from small discrete discs to large thick layers completely enveloping the lungs.
Not recognized often because adequate occupational history not obtained. Clinical presentation may simulate pleurisy of infective origin, with pain, fever, and leukocytosis, which resolves leaving widespread pleural thickening.
Or it may be benign, self—Iimiting, and not recognized by either doctor or m. The relationship of this disease to mesothelioma and lung cancer is not fully understood – few cases yet been identified.
Speculation that diffuse pleural thickening often associated with underlying interstitial disease, may be a result of unrecognized asbestos pleurisy and quite a different entity from discrete pleural plaques with no underlying disease.
[pleura: thin membrane covering each lung, lines the inner surface of the thoracic cavity]
All forms of asbestos may cause pulmonary fibrosis (asbestos related disease). The radiographic appearance of asbestosis is rather like that of other forms of pulmonary fibrosis with irregular opacities predominantly in the lower lobes. The clue relating this interstitial change to asbestos is the finding of pleural thickening or plaques.
A careful search for calcification on the diaphragm may be rewarding. The textbook description of shaggy heart border and indistinct diaphragm is rare, only in advanced cases Chest X-rays in asbestosis generally look more untidy with more aggregation eg than idiopathic (ie without apparent cause) pulmonary fibrosis.
Lung function tests classically reveal a restrictive pattern with decreased lung volumes and decreased gas transfer. Those with airways obstruction show a mixed picture. Asbestos bodies (ferruginous bodies) may be found in sputum.
They indicate exposure to asbestos but not a mark of asbestos-related disease. Rarely necessary to obtain tissue to make the diagnosis but if necessary then an open lung biopsy should be considered.
Lung function changes may precede radiological and clinical evidence and particularly in early stages, it is not uncommon to hear crackles while the chest X-ray is still normal.
Risk of smokers exposed to asbestos developing lung cancer is 50 times greater than the risk in nonsmokers with no exposure; nonsmokers with exposure have a five-fold greater risk.
Mesothelioma of the pleura is a tumor most commonly associated with asbestos exposure but many more workers will die of lung cancer. Over the past 30 years, there have been numerous epidemiological studies confirming the association between asbestos exposure and lung cancer, even in nonsmokers.
Association believed causal; rates quoted vary, depends on the method of study. Latency period 20 years, risks greater for those with higher exposure. Suggested that adenocarcinoma is most common type of tumor in asbestos workers in contrast to the general population.
Workers with evidence of significant asbestos exposure and with lung cancer are eligible for compensation. But the difficulty with smokers here who don’t have evidence of considerable exposure. Cigarettes are more likely than asbestos to cause lung cancers Matter yet to be resolved
MESOTHELIOMA OF PLEURA AND PERITONEUM:
Can develop after apparently minimal exposure, evidence that risk increases with exposure Latency maybe 30 to 40 years. Appears no connection between smoking and mesothelioma.
First symptoms of pleural mesothelioma often dull chest pain and, typically, shoulder pain. When the patient presents it’s common to find pleural effusion with weight loss, cough, and shortness of breath.
Signs depend on the stage of disease Clubbing is common and acute arthropathy has been described [disease of the joints; commonly used to imply secondary damage to joints as result of other disease processes].
Diagnosis best made by getting an accurate history of exposure and if possible finding malignant mesothelioma cells in the pleural fluid. Biopsy should be avoided. CAT scan useful for early diagnosis.
Peritoneal mesothelioma less common; usually presents late with dull pain, abdominal swelling, weight loss and ascites [fluid collection in abdominal cavity].
Exfoliative cytology [study of cells desquamated from epithelia] helps diagnosis. Very rarely more than two years; usually six months from diagnosis to death. No chemotherapy shown to be of value; treatment symptomatic.
Courtesy: Extracted from “Some notes for getting an understanding of asbestos related diseases: From John C Wagner & Kathryn McConnochie INDUSTRIAL DISEASES (The Physician, December 1983)”