the respiratory system, providing readers with essential information about these diseases, their diagnosis and their treatment. The book is structured into thematic sections, with significant overlap between some of the sections. The first two chapters provide an overview of how to identify rare diseases of the respiratory system and their differential diagnosis [2, 3]. The sections that follow cover rare diseases of the lung interstitium [4–7], rare diseases of the airways or alveoli [8–13], and rare pulmonary vascular diseases [14–17]. The authors of each chapter are experts in their respective fields, and they provide valuable insight into the diagnosis and treatment of rare respiratory diseases. For instance, chapter 3 discusses ILDs and covers differential diagnosis, definitions, clinical phenotype, radiological classifications and histological characterisation [4]. Section 4 covers rare diseases of the airways or alveoli, such as bronchiolitis [8] and alveolar proteinosis [9], as well as primary ciliary dyskinesia [10], cystic fibrosis [11], bronchiectasis [12] and α1-antitrypsin deficiency [13]. Section 5 provides a comprehensive overview of pulmonary vascular diseases, including pulmonary arterial hypertension [14], chronic thromboembolic PH [15], and PH complicating the course of other rare lung diseases [16]. The authors in this section provide clinical guidance, diagnostic and therapeutic approaches, and refer the reader to the right sources for detailed up-to-date information. Overall, this book should constitute an excellent resource for healthcare professionals, researchers and students interested in rare diseases of the respiratory system. The authors provide comprehensive coverage of the whole spectrum of rare respiratory diseases, highlighting both the progress made in recent years and the areas where more work is needed. They also promote the idea of exchange, encouraging healthcare professionals to work together and share knowledge to improve diagnostic and therapeutic options for patients with rare respiratory diseases. Authors and editors belong to and/or support the vision and mission of ERN-LUNG. This network, funded by the European Commission in 2017, is the European information and collaboration hub offering expert support to patients and professionals and will be able to connect readers who want more detailed or specific information on any topic within the field of rare diseases of the respiratory system with the respective experts. We are confident that Rare Diseases of the Respiratory System will prove a valuable resource for anyone interested in respiratory medicine. It provides a comprehensive overview of rare respiratory diseases, their diagnosis, and treatment, and promotes the exchange of knowledge among healthcare professionals. References 1 Cordier J-F, ed. Orphan Lung Diseases (ERS Monograph). Sheffield, European Respiratory Society, 2011. 2 Hebestreit H, Gahleitner F, Veldhoen S, et al. How to identify rare diseases of the respiratory system. In: Wagner TOF, Humbert M, Wijsenbeek M, et al., eds. Rare Diseases of the Respiratory System (ERS Monograph). Sheffield, European Respiratory Society, 2023 pp. 1–9. 3 Girard N. Differential diagnosis of reciprocal mimics of neoplastic and non-neoplastic pulmonary disorders: multidisciplinary approaches. In: Wagner TOF, Humbert M, Wijsenbeek M, et al., eds. Rare Diseases of the Respiratory System (ERS Monograph). Sheffield, European Respiratory Society, 2023 pp. 10–22. 4 Karampitsakos T, Wijsenbeek M, Herazo-Maya JD, et al. Interstitial lung diseases: an overview. In: Wagner TOF, Humbert M, Wijsenbeek M, et al., eds. Rare Diseases of the Respiratory System (ERS Monograph). Sheffield, European Respiratory Society, 2023 pp. 23–39. 5 Robalo Cordeiro C, Alfaro T, Freitas S. Rare interstitial lung diseases of environmental origin. In: Wagner TOF, Humbert M, Wijsenbeek M, et al., eds. Rare Diseases of the Respiratory System (ERS Monograph). Sheffield, European Respiratory Society, 2023 pp. 40–52. 6 Bomsztyk JA, Pinney JH, Lachmann HJ. Amyloidosis and the lungs and airways. In: Wagner TOF, Humbert M, Wijsenbeek M, et al., eds. Rare Diseases of the Respiratory System (ERS Monograph). Sheffield, European Respiratory Society, 2023 pp. 53–68. xii https://doi.org/10.1183/2312508X.10009923