Clinical consequences of asbestos-related diffuse pleural thickening: A review

Millions of people worldwide have been exposed to asbestos. The commonest manifestation of asbestos exposure is pleural disease, including pleural plaques and diffuse pleural thickening (DPT). Malignant mesothelioma of the pleura and DPT are less common than plaques, both conditions are likely to become more common in the future[1]. The overall prevalence of pleural disease including DPT is increasing due to the large number of workers who were exposed and the long latency of the disorder[2,3]. The Worker's Compensation Dust Diseases Board of New South Wales acknowledges an increase in DPT cases from 65 cases in 2002 to 133 cases in 2006. This review is primarily aimed at clinicians. It summarises available information on diffuse pleural thickening (DPT), contrasting it with other types of pleural disease, discusses potential pathogenetic mechanisms, and summarises available evidence regarding its clinical consequences.A link between pleural disease and asbestos exposure was first recognized in the 1930s [4] but it was not until the 1960s that a distinction between diffuse pleural thickening and pleural plaques was made[5]. Asbestos-related DPT refers to extensive fibrosis of the visceral rather than the parietal pleura, with adherence to the parietal pleura and obliteration of the pleural space (Figures 1 &2) [6,7]. In contrast, the parietal pleura is primarily involved in pleural plaques (Figure 3). DPT has unique radiographic features and significant symptomatic and functional consequences for affected patients[6]. It may cause exertional dyspnoea and has been associated with chest pain and in very rare cases with respiratory failure and death due to lung "constriction". Benign asbestos-related pleural effusions are believed to antedate the majority of cases of diffuse pleural thickening and to contribute towards disease progression. DPT may coexist with pleural plaques but has a distinctly different pathology, natural history and prognosis. Treatment is largely