Preface: Pleural Diseases Series.

Pleural diseases affect 3,000 people per million population every year. Despite its prevalence, it is only in the past 20 years that pleuralmedicine has been viewed as a specialty in its own right.1 With that, we have seen an exponential growth in research on its better management. Pleural disease is a centuries-old condition, with Hippocrates writing many landmark papers on pleural infection more than 25 centuries ago. Pleural effusion can be caused by more than 60 pathologies.2 It is a dynamic field as its incidence, diagnosis, and management constantly evolve with advances in medical management of the underlying conditions. In this issue of the Seminars of Respiratory and Critical Care Medicine, we aim to provide important updates on contemporary issues of key aspects of pleural diseases from leading experts around theworld. The enormous global economical and health care burden of pleural diseases are coming to light, as is concisely summarized by Vakil et al.3 New pleural disease entities are also described including pleural complications of COVID-19.4 With new developments of anticancer treatments, clinicians need to keep abreast of their implications on management of the associated malignant pleural effusions. Wong et al outline the impact of immunotherapy and antiangiogenic therapy on malignant effusion management,5 whereas Agrawal et al highlight the emerging intrapleural therapy for controlled of the effusions in pleural malignancies.6 Advances in biomarker discovery in mesothelioma have uncovered new clinical diagnostic tests of which clinicians should be aware.7 Manyof these targetmoleculesmay also have prognostic and therapeutic implications. Through a series of Expert Reviews, we also outline the current debates and controversies on management of spontaneous pneumothorax,8 a subject of pro–con debates in several major respiratory conferences and on advances in the care of parapneumonic effusions.9 Benign pleural effusions remain the most common cause of pleural effusions that clinicians will encounter. Porcel provides a state-ofthe-art review10 on their diagnosis and management. Muruganandan et al highlight the new advances in our understanding of why patients with pleural effusion are breathless, which is of significant interest to clinicians.11 Indwelling pleural catheters (IPCs) are now an established management of recurrent, especially malignant, pleural effusions. The focus of research has shifted from their advantages to how best to manage, or prevent, complications of IPC use.12 Sidhu et al outline the latest clinical guidelines and, where evidence is lacking, the expert opinions onbest care strategies. We trust that this series will equip clinicians with the most up-to-date knowledge on contemporary topics in pleural medicine. These advances in pleural disease will form the foundation of future, much-needed, research in clinical care of various pleural diseases.