Pneumoconiosis

No idea what this is. Never heard of this before, and I can hardly pronounce it, but it’s on my list of conditions, so let’s learn.


Pneumoconiosis

Definition: fibrosing interstitial lung disease caused by inhalation of mineral dusts (compared to EAA, which is caused by organic dusts)

Aetiology/ risk factors:

Caused by inhalation of particles of coal dust, silica or asbestos.

In complicated disease there are large nodules in the lung, consisting of dust particles (coal or silica) surrounded by layers of collagen and dying macrophages with mechanisms of damage including: direct particle cytotoxicity, excessive free radical production by macrophages and pro-inflammatory cytokines and growth factors from macrophages and epithelial cells stimulating fibroblast proliferation and eventual scarring.

Simple:

Coal worker’s pneumoconiosis (CWP) inhalation of coal dust particles over 15-20 years

Silicosisinhalation of silica particles, which are very fibrogenic. Associated with metal mining, stone quarrying, sandblasting, and pottery/ceramic manufacture.

Complicated:

Progressive Massive fibrosis (PMF) with continuous exposure, due to progression of CWP or silicosis, resulting in loss of lung function.

-Asbestosis: a pneumoconiosis in which diffuse parenchymal lung fibrosis occurs as a result of prolonged exposure to asbestos fibres. Chrysotile (white asbestos) is the least fibrogenic & crocidolite (blue asbestos) is the most fibrogenic. Amosite (brown asbestos) is least common and has intermediate fibrogenicity. Asbestos was commonly used in the building trade for fire proofing, pipe lagging, electrical wire insulation and roofing felt (builders, plumbers, electricians, shipyard workers, ship engineers). Degree of exposure is related to degree of pulmonary fibrosis.

Risk factors: occupational exposure

-Risk depends on extent of exposure, size and shape of particles and individual susceptibility, as well as co-factors such as smoking and TB.

Epidemiology: increasing incidence in developing countries

-CWP is a common dust disease in countries that have or have had underground coal-mines

Symptoms:

CWP = asymptomatic (but co-existing chronic bronchitis is common)

Silicosis = can be asymptomatic, progressive dyspnoea

Increased TB incidence

PMF = progressive dyspnoea

Cough, productive of black sputum (melanoptysis-in PMF from CWP)

Asbestosis = progressive dyspnoea, effort dyspnoea (because of pleural thickening)

                         pleuritic chest pain (acute asbestos pleurisy)

long latency period between exposure and disease (20-40 years)

Full occupational history is important as there may be long latency between exposure and disease.

Signs:

-may be normal examination

CWP or silicosis: decreased breath sounds

PMF: fibrosis (end-inspiratory crepitations), eventually cor pulmonale (raised JVP, peripheral oedema)

Asbestosis: bilateral fine end-inspiratory crepitations, clubbing

pleural effusion (stony dull percussion note with decrease vocal resonance)

Investigations:

Chest x-ray:

CWP = many small round nodular opacities (1-10mm), especially in upper zone

Compared to nodules in silicosis, the nodules in CWP tend to have less well-defined margins and a more granular appearance.

 

Example radiographs from a group of 138 West Virginian coal miners. A, Simple ...

Silicosis = characteristic eggshell calcification of hilar lymph nodes

 

Diffuse miliary or nodular pattern in upper and mid-zones

CXR of patient with silicosis, showing multiple small nodules (arrows) with upper lobe predominance

 

Image result for chest x-ray SILICOSIS EGG SHELL

‘Eggshell’ calcification in silicosis

 

-PMF = usually bilateral, upper/ mid zone large fibrotic masses (1-10 cm) that start as ill-defined/ oval opacities that develop from the periphery to the hila

PMF

Asbestosis = bilateral lower zone reticulonodular shadowing and pleural plaques, visible as white lines when calcified, often most obvious on the diaphragmatic pleura or as “holly leaf” patterns

 

Image result for chest x-ray asbestosis

CXR of patient with asbestosis, showing pleural plaques. The plaques look like continents on a world map- see Africa in the left lower zone? And on the diaphragm they are seen as white lines.

 

CT scan: fibrotic changes can be visualised early

Bronchoscopy: visualise changes, allows for bronchoalveolar lavage

Spirometry: restrictive ventilatory defect (reduced FEV1 and FVC, ratio normal or increased), impaired gas diffusion (reduced TLCO or DLCO)

Pleural biopsy– for asbestosis, to differentiate from malignant effusion

Management:

General: prevention and avoidance of exposure

-treat co-existing conditions e.g. chronic bronchitis in CWP

Medical: supportive care: oxygen, trial of inhaled steroids, treatment of complications

Patients are entitled to compensation for occupational lung diseases

Complications:

-progressive massive fibrosis, emphysema, cor pulmonale (PMF)

-Caplan’s syndrome: association between rheumatoid arthritis, pneumoconiosis, and pulmonary rheumatoid nodules

-end-stage respiratory failure (PMF)

-benign and malignant pleural effusions (asbestosis)

-bronchial adenocarcinoma (asbestosis) and mesothelioma (pleural malignancy esp. with blue asbestos/crocidolite exposure)

Prognosis: not curable. Lifespan shortened with complicated disease. Prognosis poor if malignancy develops.

References: Cheese & Onion, Rapid Medicine, Kumar and Clarke’s, Radiopaedia.org
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