Case study - A disease caused by work 25 years earlier

Plumbers, electricians, builders and shipyard workers are at risk of developing this lung condition.

Asbestosis develops 20-30 years after first exposure to asbestos (Photograph: SPL)
Asbestosis develops 20-30 years after first exposure to asbestos (Photograph: SPL)

Mr TG, a 67-year-old retired plumber, attends the surgery regularly for reviews of his hypertension and type-2 diabetes, both of which are usually well controlled. More recently, his BP had been creeping up slightly and the dose of his ACE inhibitor, ramipril, was increased with an excellent result.

Mr TG subsequently presented to the surgery complaining of a worsening cough, which he thought had started since the dose of his ramipril had been increased. On further questioning, his wife remarked that he had been coughing for the past nine to 10 months, which was when the ramipril was first started. I therefore presumed this to be an ACE inhibitor induced cough and changed his ramipril to losartan. He had never smoked and did not have a history of asthma or COPD.

Mr TG came back to see me, with his wife, six weeks later.

His cough had worsened rather than improved and they had both noticed that he was becoming more short of breath than usual when he walked uphill. The cough was a dry one. On examination I thought Mr TG had mild finger clubbing.

Respiratory examination revealed late-end expiratory crackles in both lungs. In view of this history and the fact that he was a non-smoker, I referred him for a chest X-ray and also referred him to the local respiratory physician.

I was surprised to read the letter from the clinic stating that he had asbestosis, which had been diagnosed by a high-resolution CT scan. Mr TG is currently claiming industrial injuries disablement benefit and exploring whether he is eligible for compensation, as he worked in a dockyard around 25 years ago, during which time he was exposed to asbestos.

The diagnosis
Asbestosis is one of the asbestos-related lung diseases; others include pleural plaques, pleural thickening, pleural effusions and mesothelioma. Asbestos is an insulating material that is both heat and fire resistant.

Joiners, painters, shipyard workers, builders, engineers and asbestos miners are at greatest risk of developing asbestos-related diseases.

Asbestosis is diffuse interstitial fibrosis of the lungs caused by asbestos dust. It may or may not be associated with pleural fibrosis. It develops 20 to 30 years after first exposure to asbestos and a substantial dose of asbestos is needed to cause asbestosis. This condition is related to the magnitude of exposure to asbestos.1 The asbestos fibres are inhaled and then lodge in the lungs, from where they are too large to be removed by macrophages.

Clinical presentation
The most common presenting symptom is exertional breathlessness and a reduction in exercise tolerance. Cough or wheeze are less common symptoms. It is usual for the late inspiratory fine crackles to be initially heard in the lower zones. Asbestosis is associated with finger clubbing in around four out of 10 patients.

Investigations
A chest X-ray shows irregular small opacities that are most profuse in the lower zones. Diffuse pleural thickening and/or plaques are nearly always present. However, a chest X-ray can be normal in some patients with asbestosis.

A high resolution CT scan is the investigation of choice as this will distinguish asbestosis from other causes of fibrosis. Spirometry typically shows reduced gas transfer, reduced lung volumes and a restrictive ventilatory defect.

Asbestos bodies may be found in a sputum sample or by bronchoalveolar lavage. A lung biopsy is not necessary for a diagnosis of asbestosis to be made.

Management
There is no standard treatment as asbestosis is resistant to drug treatment. All patients should avoid further exposure to asbestos and are advised to stop smoking. Patients with progressive disease may be given cortico-steroids and cyclophosphamide with limited improvement.

All patients should receive influenza and pneumococcal vaccinations.

Prognosis
Although asbestosis usually progresses slowly, in some patients it can develop more quickly.

Approximately 40 per cent of patients (most of whom have been smokers) die of lung cancer, and 10 per cent die of malignant mesothelioma.2

  • Dr Newson is a GP in the West Midlands

References
1. Wagner GR. The fallout from asbestos. Lancet 2007; 369: 973-4.

2. Coutts II, Gilson JC, Kerr IH et al. Mortality in cases of asbestosis diagnosed by a pneumoconiosis medical panel. Thorax 1987; 42: 111-16.

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