Critical Care/Respiratory CareEtiologies and Outcomes of Acute Respiratory Distress Syndrome With No Identified Common Risk FactorGibelin, Aude MD*,†,‡; Parrot, Antoine MD*,§; Fartoukh, Muriel MD, PhD*,†,‡; de Prost, Nicolas MD, PhD‡,∥Author Information *Medical and Surgical Intensive Care Unit §Pulmonology department, Assistance Publique-Hôpitaux de Paris, Hôpital Tenon, Pôle Thorax Voies aériennes, Groupe hospitalier des Hôpitaux Universitaires de l’Est Parisien †Faculté de Médecine Sorbonne Université, Paris ‡Groupe de Recherche Clinique CARMAS, Faculté de Médecine de Créteil, Université Paris Est Créteil ∥Medical Intensive Care Unit, Assistance Publique-Hôpitaux de Paris, Hôpitaux Universitaires Henri Mondor, DHU A-TVB, Créteil, France Disclosure: The authors declare that they have no conflicts of interest. Address correspondence to: Nicolas de Prost, MD, PhD, Medical and Surgical Intensive Care Unit, Hôpital Henri Mondor, 51, Avenue du Maréchal de Lattre de Tassigny, 94010 Créteil Cedex, France. E-mail: [email protected]. Clinical Pulmonary Medicine: July 2019 - Volume 26 - Issue 4 - p 108-113 doi: 10.1097/CPM.0000000000000314 Buy Metrics Abstract Almost 10% of patients with acute respiratory distress syndrome (ARDS) have no identified ARDS risk factor at ARDS diagnosis. A prompt identification of the cause of ARDS is required to initiate a targeted treatment. The purpose of this review is to delineate the main rare causes of ARDS and to provide clinicians with a pragmatic diagnostic workup. Recent epidemiological data have proposed the identification of a subgroup of ARDS patients lacking exposure to common risk factors. These can be categorized as having immune-mediated, drug-induced, malignant, and idiopathic diseases. A standardized diagnostic workup including chest imaging, the objective assessment of left-heart–filling pressures, bronchoalveolar lavage fluid microbiological investigations, and cytologic analysis, immunologic tests, and search for pneumotoxic drugs may allow for identifying the cause of ARDS in most cases. Open-lung biopsy should be considered in other cases. Copyright © 2019 Wolters Kluwer Health, Inc. All rights reserved.