Asbestosis

Question 1

Define

Answer 1

Asbestosis is diffuse interstitial fibrosis of the lung as a consequence of exposure to asbestos fibres. Disease onset occurs ≥10 years following the initial exposure to asbestos.

Question 2

What’s the aetiology?

Answer 2

The cause of asbestosis and asbestos-related pleural changes is the inhalation of asbestos fibres. Asbestos is a fibrous silicate, which exists as a naturally occurring mineral. Chrysotile is the primary asbestos mined.

When asbestos fibres are inhaled, they deposit at alveolar duct bifurcations and cause an alveolar macrophage alveolitis. These activated macrophages release cytokines, such as tumour necrosis factor and interleukin-1beta and oxidant species, which initiate a process of fibrosis. [4] The initial interstitial fibrosis typically occurs in the lower lobes and may progress to extensive fibrosis and honeycombing. Peri-bronchial fibrosis with a cellular infiltrate may narrow the airway and cause reduced air flow.

Question 3

What are the risk factors?

Answer 3

• occupational exposure
• longer duration of exposure
• smoking history

Question 4

Epidemiology

Answer 4

Asbestos use in developed countries has markedly decreased. By contrast, the amount of asbestos being used in developing countries is increasing.

Question 5

What are the presenting symptoms?

Answer 5

• dyspnoea on exertion

* cough (dry, non-productive)

Question 6

What are the signs?

Answer 6

Crackles (heard in lung bases)

Question 7

What are the appropriate investigations?

Answer 7

• Chest x-ray – interstitial fibrosis in lower zones and bilateral pleural thickening
• Pulmonary function tests – restrictive changes (may also have obstructive changes)
• High resolution CT chest
• Investigations to consider: lung biopsy or bronchial lavage