Asbestosis And The Pneumoconioses (With X rays For Better Understanding)

The pneumoconioses are occupational lung diseases caused by inhalation of a variety of industrial dusts. Strictly speaking, asbestosis is a subtype of the pneumoconioses but, because of its relative prevalence, it tends to be considered separately. Likewise, coal worker’s pneumoconiosis (CWP) merits its own discussion.
Pneumoconioses may take two forms;
• Benign forms tend to be asymptomatic. They can be recognized by the CXR appearances that they produce: small round opacities caused by perivascular collections of dust.

Small round opacities are shown by arrow in bening forms of Pneumoconioses


• Fibrotic forms produce, as the name suggests, pulmonary fibrosis associated with a restrictive lung defect. They may cause symptoms and sometimes progress to respiratory failure.

                                       Radiograph showing Progressive Massive Fibrosis

Asbestosis: The interstitial fibrosis produced by asbestos exposure is dose related, with length and level of exposure relating directly to the development and severity of symptoms. There is often a lag of 20–30 years between exposure and the development of symptoms. The fibrosis tends to be in the lower lobes and is frequently associated with pleural thickening and the appearance of pleural plaques on CXR. 

                                            Chest X ray in a patient with asbestos exposure. 

Asbestos exposure can also lead to mesothelioma and lung cancer, particularly adenocarcinoma.

Coal worker’s pneumoconiosis: CWP is seen in workers exposed to coal dust and accounts for 90% of pneumoconiosis claims for industrial compensation that are not related to asbestos exposure. The

condition is generally divided into two groups.

• Simple CWP: based on the CXR appearances of small round opacities that represent small

fibrous nodules in the lung, predominantly in the upper lobes

                        multiple small nodules shown by arrows mostly in the upper lobes. 

• Complicated CWP (progressive massive fibrosis, PMF): a patient is said to have advanced to PMF when these fibrous lesions have reached more than 3 cm in diameter. Histologically, these larger lesions commonly undergo necrosis and cavitation.

CWP associated with rheumatoid arthritis is known as Caplan’s syndrome. It is also worth noting that silicosis can also progress to PMF, and has also been associated with rheumatoid arthritis.

                                           X ray of a patient with caplan syndrome

Clinical presentation in Pneumoconioses

Symptoms include:

• breathlessness;

• cough;

• jet-black sputum production (CWP only).

Physical signs: There will be few in the early stagesof the disease, but later the patient may exhibit:

• decreased chest expansion;

• inspiratory crackles;

• wheeze (in CWP)

• clubbing (in asbestosis, but not silicosis; rarely in CWP).

Investigations

1. Chest radiograph: The International Labour Office has produced a method of classification for the radiographic changes seen in pneumoconiosis. These classifications are largely based on the size and number of opacities seen on the CXR and are used by medical panels when discussing compensation claims.

• For benign pneumoconiosis, small round opacities are diagnostic of the disease.

• Asbestos can produce a number of changes, including pleural thickening, pleural (holly leaf ) plaques, fibrosis and evidence of tumors.

CXR of a patient with previous asbestos exposure who has extensive pleural plaques

• Silicosis produces classical eggshell calcification around the hilar lymph nodes, as well as peripheral nodules. 

Coal Workers Pneumoconioses if advanced shows massive fibrosis.

CXR showing progressive massive fibrosis of CWP in a coal miner.

2. Lung function tests: These show a restrictive picture with decreased forced vital capacity, total lung capacity, residual volume and gas transfer.

3. High-resolution CT scan: Prone and supine films will help reveal the extent of the disease, and are particularly helpful when extensive pleural disease masks the lung parenchyma.

Treatment: A priority is avoidance of further dust exposure. The employers of the patient should, if necessary, consider a review of the protective equipment used by their other employees in the workplace. The benign pneumoconioses require no other treatment.

Fibrotic disease is normally considered resistant to therapy, except berylliosis, where high-dose prednisolone can produce clinical improvement. Occasionally, courses of steroids are tried in patients with asbestosis who are showing rapid deterioration of lung function.

Treatment of CWP is largely supportive.

Complications These may include:

• respiratory failure

• right heart failure

• tuberculosis in silicosis.