Aetiology of pleural plaques

Our plain-English summary of Aetiology of pleural plaques, by V. Rous, J. Studený (Thorax, 1970).

The study

• Authors: V. Rous, J. Studený
• Journal: Thorax
• Published: 1970;25(3):270-84
• Cited by: 54 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text
• In J-M's library: Johns-Manville's company medical library held a copy (J-M no. 002463).

Abstract

Pleural plaques were found in 644 (6·6%) of 9,760 photofluorograms taken in 1965 in a region of Pelhřimov district; the incidence was highest in the age group 66-70 years. The advanced age of those affected may be explained by the greater frequency of the causative agent in the past. The disorder was known in Pelhřimov district as early as 1930; it was then thought to be posttuberculous. The past history of the cases was uninformative; as a rule, the only common previous disease was pleurisy with effusion, occurring in 9·7%. The general condition of those affected was excellent; only 8% were aware of the fact that pleural lesions were present. The disorder was found mainly in farmers, familial incidence was common, and if two generations of one family suffered from the condition, the older generation was affected in 100%. Pleural plaques consist morphologically of limited areas of hyalinized collagenous connective tissue with calcium salt deposits. Tubercle bacilli could not be cultivated from the lesions. Mineralological analysis showed no evidence of silicates in the pleural plaques and a normal content in the lungs. The aetiological factor responsible for the development of pleural plaques in Pelhřimov district is not known, but asbestos cannot be implicated. The unknown noxious agent is carried to the pleura by the lymph and blood stream. Pleural plaques are an endemic disorder. The traditional view that lesions are post-tuberculous appears, in the region submitted to this study, to be a possible explanation.

In plain English

This study investigated pleural plaques (thickened, often calcified patches on the chest lining) in north-western Pelhrimov district, Czechoslovakia. In a 1965 chest X-ray survey, 9,760 of 12,245 eligible residents aged 15 and over (79%) attended, and 644 (6.6%) had plaques. Plaques were most common at ages 66 to 70. Of affected people, 9.7% recalled pleurisy with effusion and only 8% knew of their lesions. Records of 704 people with plaques showed 74 families with at least two affected members. In the article's questionnaire section, 85% of examinees with plaques named farming as their main occupation. Among 161 district autopsies on people over 15 (March to June 1968), plaques appeared in 18 of 38 (47.4%) from the study region and 13 of 123 (10.6%) elsewhere. No tuberculosis bacteria grew from plaque samples, no silicates were found in plaques, and geological surveys found no asbestos in the region. The authors concluded that the cause was unknown, that asbestos could not be implicated, and that the older view that plaques follow tuberculosis may be correct. They noted that X-rays show only some plaques found at autopsy.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Population chest X-ray (photofluorographic) survey, with autopsy and tissue studies, laboratory tests of plaque samples, and a family questionnaire
• Who was studied: Residents aged 15 and over in the north-western part of Pelhrimov district, Czechoslovakia (333 km2, population 16,178 in 1965). Of 12,245 eligible, 9,760 (79%) attended the 1965 survey. Also included were autopsies in the district (161 subjects over age 15, March to June 1968) and questionnaires sent to 704 people with pleural plaques (300 with the most complete data analysed).
• Exposure: No known asbestos exposure. The authors looked for possible causes, including asbestos, silicates, farming, and contact with tuberculous cattle. No history of contact with asbestos dust was found in the subjects studied.
• Main results:
  • Pleural plaques were found in 644 of the 9,760 people X-rayed in 1965 (6.6%).
  • Among people with plaques, the rate was highest in the age group 66 to 70 years.
  • Among people with plaques, 9.7% gave a history of pleurisy with effusion, and only 8% were aware that they had pleural lesions.
  • In the questionnaire section of the results, 85% of examinees with plaques stated that agriculture was their main occupation. The article does not state the denominator for this figure. The authors compared it with 51% of the working population of the region.
  • In records of 704 people with plaques, 74 families had at least two affected members. From this, the authors concluded that familial incidence was at least 20%.
  • In families where two generations had plaques and both parents were still alive, plaques were always found in both parents.
  • Plaques were found in about one-fifth of 161 autopsies on subjects over age 15 across the whole Pelhrimov district from March to June 1968.
  • Within those autopsies (Table III), plaques were found in 18 of 38 (47.4%) from the specially studied region and in 13 of 123 (10.6%) from the remainder of the district.
  • Tuberculosis bacteria could not be grown from the plaques.
  • Mineral analysis found no silicates in the plaques, and silicon content in the lungs was normal.
  • Geological surveys found no asbestos in any form in the region.
  • The authors examined 201 quarry and road-maintenance workers in the region. They found no asbestosis-type lung fibrosis, and the plaque rate in these workers was lower than in other inhabitants.
  • The authors stated that asbestos could not be accepted as a cause of the plaques in their series.
• The authors' conclusion: The authors concluded that the cause of pleural plaques in the district is unknown but that asbestos cannot be implicated. They considered the plaques an endemic disorder and thought an unknown agent reaches the pleura through the lymph and blood stream. They considered the traditional view that the lesions follow tuberculosis a possible explanation in this region.
• Limitations the authors state:
  • The authors acknowledged that chest X-rays show the lesion in only a proportion of the cases found at autopsy.
  • Small lesions on the chest-wall and diaphragm lining were not counted because the authors were unsure they were plaques. Later autopsies confirmed that they were.
  • Past contact with tuberculous cattle could not be determined accurately.
  • The past frequency of 'pearl disease' (tuberculous pleural beading) in cattle could only be estimated by asking long-standing residents. The authors called this an unsatisfactory method.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Pleural plaques and thickening.

Medical terms in this study, explained in our Lexicon: Pleural Plaques, Pleurisy, Silicate, Pleura, Endemic.

Related studies

• Pleural plaques and exposure to mineral fibres in a male urban necropsy population — A. Karjalainen, P.J. Karhunen, et al. (1994)
• Multiple pleural plaques. II — H.C. Anton (1968)
• Asbestos fibers and pleural plaques in a general autopsy population — A. Churg (1982)
• 'Black Spots' and hyaline pleural plaques on the parietal pleura of 150 urban necropsy cases — K. Mitchev, P. Dumortier, et al. (2002)
• A systematic review of the association between pleural plaques and changes in lung function — L. Kopylev, K.Y. Christensen, et al. (2015)
• Incidental and Underreported Pleural Plaques at Chest CT: Do Not Miss Them-Asbestos Exposure Still Exists — M.A. Mazzei, F. Contorni, et al. (2017)

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