Pleural plaques J92.9

Pleural plaques were first observed in talc workers at the end of the 19th century. In the meantime it is suspected that the talc was contaminated with asbestos.

Only around 1950 did Jakob and Bohlig recognise the connection between pleural plaques and asbestos.

Pleural plaques are circumscribed, island-like, raised widenings, approx. 5 to 10 mm thick, caused by exposure to asbestos, which are predominantly detectable in the area of the parietal pleura. They consist of collagen-rich connective tissue and often show calcification. In the course of time they increase in size.

20 years after exposure to asbestos, pleural plaques can be detected radiologically in about 1.1% of those affected. 40 years after exposure, these plaques can already be found in 58 % of those affected.

The presence of the plaques does not necessarily allow a conclusion to be drawn about the duration and extent of the asbestos exposure. The same applies to the development of asbestos-related malignancies of the lung or pleura, here too the extent of exposure is irrelevant.

These plaques can occur even after slight and single contact with fibrous dusts. They can be found in exposed workers, but also in non-exposed family members (especially female spouses - presumably due to laundry contact of work clothes) and also in persons living in the vicinity of asbestos-emitting factories.

Plaques are primarily caused by exposure to asbestos. They appear at the earliest about 20 years after exposure (but there are also cases of 40 years post-exposure describe). The plaques do not allow any conclusion to be drawn about possible pulmonary damage.

In addition to asbestos, there are other fibrous dusts, such as erionite or artificial mineral fibres, which are capable of causing plaques. In addition, pleural plaques occur in conditions following empyema, tuberculosis, rib fractures, haematothorax, radiation and tumour diseases.

Pleural plaques do not cause any complaints.

The sometimes described stress dyspnea cannot be explained by the plaques. It is most likely to be due to pulmonary asbestosis and the associated "pulmonary rigidity".

X-ray

In the early stages, it is difficult to make a radiological diagnosis, as the pleura is often only visible with milky diffuse thickening. As soon as the plaques have reached a size of at least 5 mm, they can be visualized radiologically. Calcifications in the plaques are generally easier to visualize.

Along the parietal pleura, plaques can be detected by calcifications, especially in the area of the lower lung fields, the diaphragm and the mediastinum. Their distribution is irregular and can be unilateral or bilateral.

Changes in the area of the diaphragm are characteristic. However, the sinus is never affected.

The sensitivity of the conventional X-ray image is, however, quite low (approx. 28 %). The specificity is significantly higher at 80 % to 100 %. False-positive results were found in 20 %, because radiologically plaques are not so easily distinguished from subpleural fat deposits.

HRCT

The HRCT (High-Resolution-CT) is the most sensitive examination method for the detection of plaques. It also allows the differentiation between plaques and subpleural fat accumulation.

Lung function

In the lung function, a slight reduction of the vital capacity is usually observed.

Disturbances of gas exchange and diffusion capacity are not found.

Laboratory

The usual laboratory values show no abnormalities, in particular no signs of inflammation. Occasionally there is a reduced activity of T-lymphocytes and an increase in antinuclear antibodies (ANA).

Thoracoscopy

It is by far the most sensitive of all examination techniques. However, the indication for thoracoscopy should only be given if the diagnosis remains unclear despite the exhaustion of all non-invasive methods.

It is not at all uncommon for pleural plaques to be a chance finding during a thoracoscopy performed for other reasons.

Lavage

In the lavage, asbestos corpuscles are found in 50 % of the plaque-bearing bodies. However, these are not present in such high concentrations as in pulmonary asbestosis.

• Subpleural fat deposits

The risk of developing bronchial carcinoma in persons with pleural plaques and asbestos contamination is estimated to be 2 to 3 times higher than in persons with asbestos contamination, but without evidence of plaques, assuming the same smoking habits in both groups.

1. Herold G et al (2017) Internal Medicine S 397
2. Kasper DL et al (2015) Harrison's Principles of Internal Medicine S 308e-15, 1689
3. Kasper DL et al (2015) Harrison's Internal Medicine S 2064
4. Konietzko N et al (1992) Asbestos and lungs S 91-100
5. Loscalzo J et al (2011) Harrison's Lung Medicine and Intensive Care S 102