Pneumothorax refers to the abnormal presence of air in the pleural space. The diagnosis is usually clinical based on the status of the patient, However, chest radiograph exhibits characteristic features aiding the diagnosis of pneumothorax. The commonly present features are: - absent lung markings on affected side - radiolucent peripheral space - visible visceral pleural edge - atelectasis may or may not be present - subcutaneous emphysema may or may not be present - shifting of mediastinum Reference: https://radiopaedia.org/articles/pneumothorax Image via: https://radiopaedia.org/articles/pneumothorax